diff --git a/bin/tools/RunFunctions b/bin/tools/RunFunctions
index a0f439fab1..b22c451c40 100644
--- a/bin/tools/RunFunctions
+++ b/bin/tools/RunFunctions
@@ -25,6 +25,12 @@
 # Basic sanity checks
 [ -d "$FOAM_TUTORIALS" ] || echo "No OpenFOAM tutorials? : $FOAM_TUTORIALS" 1>&2
 
+# Darwin workaround - SIP clearing DYLD_LIBRARY_PATH variable
+if [ -n "$FOAM_DYLD_LIBRARY_PATH" ] && [ -z "$DYLD_LIBRARY_PATH" ]
+then
+    export DYLD_LIBRARY_PATH="$FOAM_DYLD_LIBRARY_PATH"
+fi
+
 
 #------------------------------------------------------------------------------
 
diff --git a/bin/tools/foamConfigurePaths b/bin/tools/foamConfigurePaths
index 27677be6bb..3d47960ad3 100755
--- a/bin/tools/foamConfigurePaths
+++ b/bin/tools/foamConfigurePaths
@@ -7,7 +7,7 @@
 #    \\/     M anipulation  |
 #------------------------------------------------------------------------------
 #     Copyright (C) 2011-2016 OpenFOAM Foundation
-#     Copyright (C) 2016-2020 OpenCFD Ltd.
+#     Copyright (C) 2016-2021 OpenCFD Ltd.
 #------------------------------------------------------------------------------
 # License
 #     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -42,11 +42,11 @@ printHelp() {
 Obsolete options:
   -foamInstall DIR    [obsolete]
   -projectName NAME   [obsolete]
-  -sigfpe|-no-sigfpe  [obsolete - now under etc/controlDict]
-  -archOption 32|64   [obsolete setting of 'WM_ARCH_OPTION' - edit manually]
+  -sigfpe|-no-sigfpe  [obsolete] now under etc/controlDict
+  -archOption 32|64   [obsolete] now edit WM_ARCH_OPTION manually
 
 Equivalent options:
-  -version -foamVersion --projectVersion
+  -version              --projectVersion | -foamVersion
   -archOption           --archOption
   -third                -ThirdParty
   -paraview             --paraviewVersion | -paraviewVersion
@@ -55,6 +55,8 @@ Equivalent options:
   -scotch-path          --scotchArchPath | -scotchArchPath
   -system-compiler      -system
   -third-compiler       -third
+  -sys-openmpi          -openmpi-system
+  -openmpi              -openmpi-third
 
 HELP_COMPAT
         exit 0 # A clean exit
@@ -89,10 +91,9 @@ Compiler
   mpc-VERSION         For ThirdParty gcc (mpc-system for system library)
 
 MPI
-  -mpi NAME           specify 'WM_MPLIB' type (eg, INTELMPI, etc)
-  -openmpi VER        use ThirdParty openmpi, with version for 'FOAM_MPI'
-  -openmpi-system     use system openmpi
-  -openmpi-third      use ThirdParty openmpi (using default version)
+  -mpi=NAME           Specify 'WM_MPLIB' type (eg, INTELMPI, etc)
+  -openmpi[=VER]      Use ThirdParty openmpi, with version for 'FOAM_MPI'
+  -sys-openmpi[=MAJ]  Use system openmpi, with specified major version
 
 Components versions (ThirdParty)
   -adios VER          specify 'adios2_version'
@@ -120,12 +121,12 @@ Components specified by absolute path
   -scotch-path DIR    Path for 'SCOTCH_ARCH_PATH' (overrides -scotch)
 
 Graphics
-  -paraview VER       specify 'ParaView_VERSION' (eg, 5.4.1 or system)
+  -paraview VER       specify 'ParaView_VERSION' (eg, 5.9.0 or system)
   -paraview-qt VER    specify 'ParaView_QT' (eg, qt-system)
-  -paraview-path DIR  specify 'ParaView_DIR' (eg, /opt/ParaView-5.4.1)
+  -paraview-path DIR  specify 'ParaView_DIR' (eg, /opt/ParaView-5.9.0)
   -llvm VER           specify 'mesa_llvm'
   -mesa VER           specify 'mesa_version' (eg, mesa-13.0.1)
-  -vtk  VER           specify 'vtk_version' (eg, VTK-7.1.0)
+  -vtk  VER           specify 'vtk_version' (eg, VTK-9.0.0)
   -llvm-path DIR      Path for 'LLVM_ARCH_PATH'   (overrides -llvm)
   -mesa-path DIR      Path for 'MESA_ARCH_PATH'   (overrides -mesa)
   -vtk-path DIR       Path for 'VTK_DIR'          (overrides -vtk)
@@ -212,12 +213,13 @@ _inlineSed()
     # Local filename (for reporting)
     localFile="$(echo "$file" | sed -e "s#^$projectDir/##")"
 
-    grep -q "$regexp" "$file" && sed -i -e "$cmd" "$file" || { \
+    if grep -q "$regexp" "$file" && sed -i -e "$cmd" "$file"
+    then
+        [ -n "$msg" ] && echo "    $msg  ($localFile)"
+    else
         echo "Failed: ${msg:-replacement} in $localFile"
         return 1
-    }
-
-    [ -n "$msg" ] && echo "    $msg  ($localFile)"
+    fi
 
     return 0
 }
@@ -278,8 +280,8 @@ replaceEtc()
     local file="$1"
     shift
 
-    file=$(_foamEtc "$file")
-    replace $file "$@"
+    file="$(_foamEtc "$file")"
+    replace "$file" "$@"
 }
 
 
@@ -289,24 +291,36 @@ replaceEtcCsh()
     local file="$1"
     shift
 
-    file=$(_foamEtc "$file")
-    replaceCsh $file "$@"
+    file="$(_foamEtc "$file")"
+    replaceCsh "$file" "$@"
 }
 
 
 # Get the option's value (argument), or die on missing or empty argument
 # $1 option
 # $2 value
+
+# Returns values via optValue, nOptArgs variables!!
+optValue=""
+nOptArgs=0  # The number of args to shift
+
 getOptionValue()
 {
-    local value="$2"
-    [ -n "$value" ] || die "'$1' option requires an argument"
+    optValue="${1#*=}"
+    if [ "$optValue" = "$1" ]
+    then
+        # Eg, -option value
+        optValue="$2"
+        [ -n "$optValue" ] || die "'$1' option requires an argument"
+        nOptArgs=1
+    else
+        # Eg, -option=value
+        nOptArgs=0
+    fi
 
     # Remove any surrounding double quotes
-    value="${value%\"}"
-    value="${value#\"}"
-
-    echo "$value"
+    optValue="${optValue%\"}"
+    optValue="${optValue#\"}"
 }
 
 
@@ -366,7 +380,7 @@ removeCshMagic()
 
 #------------------------------------------------------------------------------
 
-unset adjusted optMpi
+unset adjusted
 # Parse options
 while [ "$#" -gt 0 ]
 do
@@ -421,26 +435,37 @@ CONFIG_CSH
         [ -n "$FOAM_CONFIG_ETC" ] || unset FOAM_CONFIG_ETC
         ;;
 
-   -project-path)
+   -project-path=* | -project-path)
         # Replace WM_PROJECT_DIR=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc     bashrc  WM_PROJECT_DIR "\"$optionValue\""
-        replaceEtcCsh  cshrc   WM_PROJECT_DIR "\"$optionValue\""
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
 
-        removeBashMagic $(_foamEtc bashrc)
-        removeCshMagic  $(_foamEtc cshrc)
+        if [ -n "$optValue" ]
+        then
+            replaceEtc     bashrc  WM_PROJECT_DIR "\"$optValue\""
+            replaceEtcCsh  cshrc   WM_PROJECT_DIR "\"$optValue\""
 
-        adjusted=true
-        shift
+            removeBashMagic "$(_foamEtc bashrc)"
+            removeCshMagic  "$(_foamEtc cshrc)"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
-   -version | -foamVersion | --projectVersion)
+   -version=* | -version | -foamVersion | --projectVersion)
         # Replace WM_PROJECT_VERSION=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc     bashrc  WM_PROJECT_VERSION "$optionValue"
-        replaceEtcCsh  cshrc   WM_PROJECT_VERSION "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc     bashrc  WM_PROJECT_VERSION "$optValue"
+            replaceEtcCsh  cshrc   WM_PROJECT_VERSION "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -sp | -SP | -float32)
@@ -466,131 +491,168 @@ CONFIG_CSH
 
     -int32 | -int64)
         # Replace WM_LABEL_SIZE=...
-        optionValue="${1#-int}"
-        replaceEtc     bashrc  WM_LABEL_SIZE "$optionValue"
-        replaceEtcCsh  cshrc   WM_LABEL_SIZE "$optionValue"
+        optValue="${1#-int}"
+        replaceEtc     bashrc  WM_LABEL_SIZE "$optValue"
+        replaceEtcCsh  cshrc   WM_LABEL_SIZE "$optValue"
         adjusted=true
         ;;
 
 
 ## Compiler ##
 
-    -clang)
+    -clang=* | -clang)
         # Replace default_clang_version=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/compiler   default_clang_version "$optionValue"
-        replaceEtc  config.csh/compiler  default_clang_version "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/compiler   default_clang_version "$optValue"
+            replaceEtc  config.csh/compiler  default_clang_version "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
-    -gcc)
+    -gcc=* | -gcc)
         # Replace default_gcc_version=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/compiler   default_gcc_version "$optionValue"
-        replaceEtc  config.csh/compiler  default_gcc_version "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/compiler   default_gcc_version "$optValue"
+            replaceEtc  config.csh/compiler  default_gcc_version "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -system-compiler | -system)
         # Replace WM_COMPILER_TYPE=... and WM_COMPILER=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  bashrc  \
-            WM_COMPILER_TYPE system \
-            WM_COMPILER "$optionValue"
-        replaceEtcCsh  cshrc \
-            WM_COMPILER_TYPE system \
-            WM_COMPILER "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  bashrc  \
+                WM_COMPILER_TYPE system \
+                WM_COMPILER "$optValue"
+            replaceEtcCsh  cshrc \
+                WM_COMPILER_TYPE system \
+                WM_COMPILER "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -third-compiler | -third | -ThirdParty)
         # Replace WM_COMPILER_TYPE=... and WM_COMPILER=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  bashrc  \
-            WM_COMPILER_TYPE ThirdParty \
-            WM_COMPILER "$optionValue"
-        replaceEtcCsh  cshrc  \
-            WM_COMPILER_TYPE ThirdParty \
-            WM_COMPILER "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  bashrc  \
+                WM_COMPILER_TYPE ThirdParty \
+                WM_COMPILER "$optValue"
+            replaceEtcCsh  cshrc  \
+                WM_COMPILER_TYPE ThirdParty \
+                WM_COMPILER "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     gmp-[4-9]* | gmp-system)
         # gcc-related package
-        replaceEtc  config.sh/compiler   default_gmp_version "$1"
-        replaceEtc  config.csh/compiler  default_gmp_version "$1"
+        optValue="${1#-}"
+        replaceEtc  config.sh/compiler   default_gmp_version "$optValue"
+        replaceEtc  config.csh/compiler  default_gmp_version "$optValue"
         adjusted=true
         ;;
 
     mpfr-[2-9]* | mpfr-system)
         # gcc-related package
-        replaceEtc  config.sh/compiler   default_mpfr_version "$1"
-        replaceEtc  config.csh/compiler  default_mpfr_version "$1"
+        optValue="${1#-}"
+        replaceEtc  config.sh/compiler   default_mpfr_version "$optValue"
+        replaceEtc  config.csh/compiler  default_mpfr_version "$optValue"
         adjusted=true
         ;;
 
     mpc-[0-9]* | mpc-system)
         # gcc-related package
-        replaceEtc  config.sh/compiler   default_mpc_version "$1"
-        replaceEtc  config.csh/compiler  default_mpc_version "$1"
+        optValue="${1#-}"
+        replaceEtc  config.sh/compiler   default_mpc_version "$optValue"
+        replaceEtc  config.csh/compiler  default_mpc_version "$optValue"
         adjusted=true
         ;;
 
 
 ## MPI ##
 
-    -mpi)
+    -mpi=* | -mpi)
         # Explicitly set WM_MPLIB=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc     bashrc  WM_MPLIB "$optionValue"
-        replaceEtcCsh  cshrc   WM_MPLIB "$optionValue"
-        optMpi=system
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc     bashrc  WM_MPLIB "$optValue"
+            replaceEtcCsh  cshrc   WM_MPLIB "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
-    -openmpi)
-        # Replace FOAM_MPI=openmpi-<digits>.. and set to use third-party
-        #  The edit is slightly fragile, but works
-        expected="openmpi-[1-9][.0-9]*"
-        optMpi=$(getOptionValue "$@")
-
-        _matches "$optMpi" "$expected" || \
-            die "'$1' has bad value: '$optMpi'"
-
-        _inlineSed  $(_foamEtc config.sh/mpi) \
-            "FOAM_MPI=$expected" \
-            "FOAM_MPI=$optMpi" \
-            "Replaced 'FOAM_MPI=$expected' by 'FOAM_MPI=$optMpi'"
-
-        _inlineSed  $(_foamEtc config.csh/mpi) \
-            "FOAM_MPI $expected" \
-            "FOAM_MPI $optMpi" \
-            "Replaced 'FOAM_MPI $expected' by 'FOAM_MPI $optMpi'"
-
-        replaceEtc     bashrc  WM_MPLIB OPENMPI
-        replaceEtcCsh  cshrc   WM_MPLIB OPENMPI
-        adjusted=true
-        shift
-        ;;
-
-    -openmpi-system)
+    -sys-openmpi=* | -sys-openmpi | -openmpi-system)
+        optValue="$(echo "$1" | sed -ne 's/^.*mpi=\([1-9][0-9]*\).*/\1/p')"
         # Explicitly set WM_MPLIB=SYSTEMOPENMPI
-        replaceEtc     bashrc  WM_MPLIB SYSTEMOPENMPI
-        replaceEtcCsh  cshrc   WM_MPLIB SYSTEMOPENMPI
-        optMpi=system
-        adjusted=true
+        if [ -n "$optValue" ]
+        then
+            replaceEtc     bashrc  WM_MPLIB SYSTEMOPENMPI"$optValue"
+            replaceEtcCsh  cshrc   WM_MPLIB SYSTEMOPENMPI"$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
-    -openmpi-third)
-        # Explicitly set WM_MPLIB=OPENMPI, using default setting for openmpi
+    -openmpi=* | -openmpi | -openmpi-third)
+        # Explicitly set WM_MPLIB=OPENMPI
+        # - use default setting for openmpi, or
+        #  replace FOAM_MPI=openmpi-<digits>..
+        #  The edit is slightly fragile, but works
+
+        expected="openmpi-[1-9][.0-9]*"
+        optValue="$(echo "$1" | sed -ne 's/^.*mpi=//p')"
+        if [ -n "$optValue" ]
+        then
+             if [ "${optValue#openmpi-}" = "$optValue" ]
+             then
+                 optValue="openmpi-$optValue"
+             fi
+
+            _matches "$optValue" "$expected" || \
+                die "'${1%=*}' has bad value: '$optValue'"
+
+            _inlineSed  "$(_foamEtc config.sh/mpi)" \
+                "FOAM_MPI=$expected" \
+                "FOAM_MPI=$optValue" \
+                "Replaced 'FOAM_MPI=$expected' by 'FOAM_MPI=$optValue'"
+
+            _inlineSed  "$(_foamEtc config.csh/mpi)" \
+                "FOAM_MPI=$expected" \
+                "FOAM_MPI=$optValue" \
+                "Replaced 'FOAM_MPI $expected' by 'FOAM_MPI $optValue'"
+        fi
         replaceEtc     bashrc  WM_MPLIB OPENMPI
         replaceEtcCsh  cshrc   WM_MPLIB OPENMPI
-        optMpi=third
         adjusted=true
         ;;
 
@@ -599,146 +661,242 @@ CONFIG_CSH
 
     -adios | -adios2)
         # Replace adios2_version=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/adios2   adios2_version "$optionValue"
-        replaceEtc  config.csh/adios2  adios2_version "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/adios2   adios2_version "$optValue"
+            replaceEtc  config.csh/adios2  adios2_version "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -adios-path | -adios2-path)
         # Replace ADIOS2_ARCH_PATH=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc     config.sh/adios2   ADIOS2_ARCH_PATH "\"$optionValue\""
-        replaceEtcCsh  config.csh/adios2  ADIOS2_ARCH_PATH "\"$optionValue\""
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc     config.sh/adios2   ADIOS2_ARCH_PATH "\"$optValue\""
+            replaceEtcCsh  config.csh/adios2  ADIOS2_ARCH_PATH "\"$optValue\""
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -boost)
         # Replace boost_version=...  (config is cgal or CGAL)
-        optionValue=$(getOptionValue "$@")
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
         cfgName=cgal; _foamEtc -q config.sh/"$cfgName" || cfgName=CGAL
-        replaceEtc  config.sh/"$cfgName"   boost_version "$optionValue"
-        replaceEtc  config.csh/"$cfgName"  boost_version "$optionValue"
-        adjusted=true
-        shift
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/"$cfgName"   boost_version "$optValue"
+            replaceEtc  config.csh/"$cfgName"  boost_version "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -boost-path)
         # Replace BOOST_ARCH_PATH=...  (config is cgal or CGAL)
-        optionValue=$(getOptionValue "$@")
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
         cfgName=cgal; _foamEtc -q config.sh/"$cfgName" || cfgName=CGAL
-        replaceEtc  config.sh/"$cfgName"   BOOST_ARCH_PATH "\"$optionValue\""
-        replaceEtc  config.csh/"$cfgName"  BOOST_ARCH_PATH "\"$optionValue\""
-        adjusted=true
-        shift
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/"$cfgName"   BOOST_ARCH_PATH "\"$optValue\""
+            replaceEtc  config.csh/"$cfgName"  BOOST_ARCH_PATH "\"$optValue\""
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -cgal)
         # Replace cgal_version=...  (config is cgal or CGAL)
-        optionValue=$(getOptionValue "$@")
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
         cfgName=cgal; _foamEtc -q config.sh/"$cfgName" || cfgName=CGAL
-        replaceEtc  config.sh/"$cfgName"   cgal_version "$optionValue"
-        replaceEtc  config.csh/"$cfgName"  cgal_version "$optionValue"
-        adjusted=true
-        shift
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/"$cfgName"   cgal_version "$optValue"
+            replaceEtc  config.csh/"$cfgName"  cgal_version "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -cgal-path)
         # Replace CGAL_ARCH_PATH=...  (config is cgal or CGAL)
-        optionValue=$(getOptionValue "$@")
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
         cfgName=cgal; _foamEtc -q config.sh/"$cfgName" || cfgName=CGAL
-        replaceEtc     config.sh/"$cfgName"   CGAL_ARCH_PATH "$optionValue"
-        replaceEtcCsh  config.csh/"$cfgName"  CGAL_ARCH_PATH "$optionValue"
-        adjusted=true
-        shift
+        if [ -n "$optValue" ]
+        then
+            replaceEtc     config.sh/"$cfgName"   CGAL_ARCH_PATH "$optValue"
+            replaceEtcCsh  config.csh/"$cfgName"  CGAL_ARCH_PATH "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -fftw)
         # Replace fftw_version=...
-        optionValue=$(getOptionValue "$@")
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
         # config.sh/fftw or config.sh/FFTW
         cfgName=fftw; _foamEtc -q config.sh/"$cfgName" || cfgName=FFTW
-        replaceEtc  config.sh/"$cfgName"   fftw_version "$optionValue"
-        replaceEtc  config.csh/"$cfgName"  fftw_version "$optionValue"
-        adjusted=true
-        shift
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/"$cfgName"   fftw_version "$optValue"
+            replaceEtc  config.csh/"$cfgName"  fftw_version "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -fftw-path)
         # Replace FFTW_ARCH_PATH=...
-        optionValue=$(getOptionValue "$@")
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
         # config.sh/fftw or config.sh/FFTW
         cfgName=fftw; _foamEtc -q config.sh/"$cfgName" || cfgName=FFTW
-        replaceEtc     config.sh/"$cfgName"  FFTW_ARCH_PATH "\"$optionValue\""
-        replaceEtcCsh  config.csh/"$cfgName" FFTW_ARCH_PATH "\"$optionValue\""
-        adjusted=true
-        shift
+        if [ -n "$optValue" ]
+        then
+            replaceEtc     config.sh/"$cfgName"  FFTW_ARCH_PATH "\"$optValue\""
+            replaceEtcCsh  config.csh/"$cfgName" FFTW_ARCH_PATH "\"$optValue\""
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -cmake)
         # Replace cmake_version=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/cmake   cmake_version "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/cmake   cmake_version "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -cmake-path)
         # Replace CMAKE_ARCH_PATH=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/cmake   CMAKE_ARCH_PATH "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/cmake   CMAKE_ARCH_PATH "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -kahip)
         # Replace KAHIP_VERSION=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/kahip  KAHIP_VERSION "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/kahip  KAHIP_VERSION "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -kahip-path)
         # Replace KAHIP_ARCH_PATH=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/kahip  KAHIP_ARCH_PATH "\"$optionValue\""
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/kahip  KAHIP_ARCH_PATH "\"$optValue\""
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -metis)
         # Replace METIS_VERSION=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/metis  METIS_VERSION "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/metis  METIS_VERSION "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -metis-path)
         # Replace METIS_ARCH_PATH=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/metis  METIS_ARCH_PATH "\"$optionValue\""
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/metis  METIS_ARCH_PATH "\"$optValue\""
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -scotch | -scotchVersion | --scotchVersion)
         # Replace SCOTCH_VERSION=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/scotch  SCOTCH_VERSION "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/scotch  SCOTCH_VERSION "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -scotch-path | -scotchArchPath | --scotchArchPath)
         # Replace SCOTCH_ARCH_PATH=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/scotch  SCOTCH_ARCH_PATH "\"$optionValue\""
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/scotch  SCOTCH_ARCH_PATH "\"$optValue\""
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
 
@@ -747,107 +905,156 @@ CONFIG_CSH
     -paraview | -paraviewVersion | --paraviewVersion)
         # Replace ParaView_VERSION=...
         expected="[5-9][.0-9]*"  # but also accept system
-        optionValue=$(getOptionValue "$@")
-        _matches "$optionValue" "$expected" || \
-            [ "$optionValue" != "${optionValue%system}" ] || \
-            die "'$1' has bad value: '$optionValue'"
-        replaceEtc  config.sh/paraview   ParaView_VERSION "$optionValue"
-        replaceEtc  config.csh/paraview  ParaView_VERSION "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        _matches "$optValue" "$expected" || \
+            [ "$optValue" != "${optValue%system}" ] || \
+            die "'${1%=*}' has bad value: '$optValue'"
+
+        shift "${nOptArgs:-0}"
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/paraview   ParaView_VERSION "$optValue"
+            replaceEtc  config.csh/paraview  ParaView_VERSION "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -paraview-qt)
         # Replace ParaView_QT=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/paraview   ParaView_QT "$optionValue"
-        replaceEtc  config.csh/paraview  ParaView_QT "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/paraview   ParaView_QT "$optValue"
+            replaceEtc  config.csh/paraview  ParaView_QT "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -paraview-path | -paraviewInstall | --paraviewInstall)
         # Replace ParaView_DIR=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc     config.sh/paraview   ParaView_DIR \""$optionValue\""
-        replaceEtcCsh  config.csh/paraview  ParaView_DIR \""$optionValue\""
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc     config.sh/paraview   ParaView_DIR \""$optValue\""
+            replaceEtcCsh  config.csh/paraview  ParaView_DIR \""$optValue\""
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -llvm)
         # Replace mesa_llvm=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/vtk   mesa_llvm "$optionValue"
-        replaceEtc  config.csh/vtk  mesa_llvm "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/vtk   mesa_llvm "$optValue"
+            replaceEtc  config.csh/vtk  mesa_llvm "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -mesa)
         # Replace mesa_version=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/vtk   mesa_version "$optionValue"
-        replaceEtc  config.csh/vtk  mesa_version "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/vtk   mesa_version "$optValue"
+            replaceEtc  config.csh/vtk  mesa_version "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -vtk)
         # Replace vtk_version=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc  config.sh/vtk   vtk_version "$optionValue"
-        replaceEtc  config.csh/vtk  vtk_version "$optionValue"
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc  config.sh/vtk   vtk_version "$optValue"
+            replaceEtc  config.csh/vtk  vtk_version "$optValue"
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -llvm-path)
         # Replace LLVM_ARCH_PATH=...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc     config.sh/vtk   LLVM_ARCH_PATH \""$optionValue\""
-        replaceEtcCsh  config.csh/vtk  LLVM_ARCH_PATH \""$optionValue\""
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc     config.sh/vtk   LLVM_ARCH_PATH \""$optValue\""
+            replaceEtcCsh  config.csh/vtk  LLVM_ARCH_PATH \""$optValue\""
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -mesa-path)
         # Replace MESA_ARCH_PATH...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc     config.sh/vtk   MESA_ARCH_PATH \""$optionValue\""
-        replaceEtcCsh  config.csh/vtk  MESA_ARCH_PATH \""$optionValue\""
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc     config.sh/vtk   MESA_ARCH_PATH \""$optValue\""
+            replaceEtcCsh  config.csh/vtk  MESA_ARCH_PATH \""$optValue\""
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
     -vtk-path)
         # Replace VTK_DIR...
-        optionValue=$(getOptionValue "$@")
-        replaceEtc     config.sh/vtk   VTK_DIR \""$optionValue\""
-        replaceEtcCsh  config.csh/vtk  VTK_DIR \""$optionValue\""
-        adjusted=true
-        shift
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
+
+        if [ -n "$optValue" ]
+        then
+            replaceEtc     config.sh/vtk   VTK_DIR \""$optValue\""
+            replaceEtcCsh  config.csh/vtk  VTK_DIR \""$optValue\""
+            adjusted=true
+        else
+            : "${adjusted:=empty}"
+        fi
         ;;
 
 
 ## Misc ##
 
+    # Obsolete flags
     -sigfpe | -no-sigfpe)
         echo "Enable/disable FOAM_SIGFPE now via controlDict" 1>&2
         ;;
 
-    -archOption | --archOption)
-        # Replace WM_ARCH_OPTION=...
-        optionValue=$(getOptionValue "$@")
-        echo "Ignoring $1 option: no longer supported" 1>&2
-        shift
-        ;;
-
+    # Obsolete options
+    -archOption | --archOption | \
     -foamInstall | --foamInstall | -projectName | --projectName)
-        # Removed for 1812
-        optionValue=$(getOptionValue "$@")
-        echo "Ignoring $1 option: obsolete" 1>&2
-        shift
+        echo "Ignoring obsolete option: $1" 1>&2
+        getOptionValue "$@"
+        shift "${nOptArgs:-0}"
         ;;
 
     *)
diff --git a/etc/config.csh/functions b/etc/config.csh/functions
index 71bc08f76c..eb0b6bf054 100644
--- a/etc/config.csh/functions
+++ b/etc/config.csh/functions
@@ -27,7 +27,7 @@
 #     _foamClean     : eval call to foamCleanPath for specific shell
 #     _foamEcho      : silent/non-silent echo
 #     _foamEtc       : resolve etc files (silent or verbose)
-#     _foamAddPath   : prepend to MANPATH
+#     _foamAddPath   : prepend to PATH
 #     _foamAddMan    : prepend to MANPATH
 #     _foamAddLib    : prepend to [DY]LD_LIBRARY_PATH
 #     _foamAddLibAuto: call to lib-dir for lib64/lib resolved name
diff --git a/etc/config.csh/mpi b/etc/config.csh/mpi
index d69122a946..c43c97568c 100644
--- a/etc/config.csh/mpi
+++ b/etc/config.csh/mpi
@@ -49,7 +49,7 @@
 unsetenv MPI_HOME
 setenv FOAM_MPI dummy  # Fallback value
 setenv MPI_ARCH_PATH   # Empty, but defined
-set _foamMpiVersion    # Track mpi (major) version as required
+set _foamMpiVersion    # Track mpi version as required
 
 # Location for ThirdParty installations
 set _foamMpiPrefixDir="$WM_THIRD_PARTY_DIR/platforms/$WM_ARCH$WM_COMPILER"
@@ -59,18 +59,28 @@ set _foamMpiWarning="openfoam (etc/config.csh/mpi) => "  # Prefix for warnings
 
 switch ("$WM_MPLIB")
 
-# The system openmpi, discover locations via <mpicc>
+# ----
+# The system openmpi, discover locations by orte-info, mpicc or orterun
+# Preserve major or full version for the naming
+case sys-openmpi[1-9]:
+case sys-openmpi-[1-9]*:
 case SYSTEMOPENMPI[1-9]:
-    # Preserve major version for the naming
-    set _foamMpiVersion=`echo "$WM_MPLIB" | sed -e 's#^.*MPI##'`
-    #[fallthrough]
+case SYSTEMOPENMPI-[1-9]*:
+    # Preserve version or full version for the naming
+    set _foamMpiVersion=`echo "$WM_MPLIB" | sed -e 's#^.*MPI##i'`
+    #[[fallthrough]]
 
+case sys-openmpi:
 case SYSTEMOPENMPI:
     setenv FOAM_MPI "sys-openmpi${_foamMpiVersion}"
+    setenv WM_MPLIB "SYSTEMOPENMPI${_foamMpiVersion}"
+
+    # Undefine OPAL_PREFIX if set to one of the paths on foamOldDirs?
     _foamEtc -config prefs.sys-openmpi  ## Optional adjustments
 
-    # MPI_ARCH_PATH (prefs) if a valid dir, or discover via <mpicc>
+    # MPI_ARCH_PATH (prefs) if a valid dir, or need to discover
     if ( -d "$MPI_ARCH_PATH" ) then
+        _foamAddPath    "$MPI_ARCH_PATH"/bin
         _foamAddLibAuto "$MPI_ARCH_PATH"
     else
         setenv MPI_ARCH_PATH
@@ -139,8 +149,21 @@ case SYSTEMOPENMPI:
     breaksw
 
 
+# ----
+case openmpi:
+case openmpi-[1-9]*:
 case OPENMPI:
+case OPENMPI-[1-9]*:
     setenv FOAM_MPI openmpi-4.0.3
+
+    ## Add version embedded in the naming
+    set _foamMpiVersion=`echo "$WM_MPLIB" | sed -e 's#[^-]*-##'`
+    if ( "$_foamMpiVersion" != "$WM_MPLIB" ) then
+        setenv FOAM_MPI "openmpi-${_foamMpiVersion}"
+        setenv WM_MPLIB "OPENMPI-${_foamMpiVersion}"
+    else
+        setenv WM_MPLIB OPENMPI
+    endif
     _foamEtc -config prefs.openmpi  ## Optional adjustments
 
     # MPI_ARCH_PATH (prefs) if a valid dir, or ThirdParty location
@@ -159,6 +182,7 @@ case OPENMPI:
     breaksw
 
 
+# ----
 # Arbitrary, user-specified mpi implementation
 # - used by spack, which populates appropriate wmake rules
 case USERMPI:
@@ -167,14 +191,18 @@ case USERMPI:
     breaksw
 
 
+# ----
 # EasyBuild handles everything via <mpicc>
 case EASYBUILDMPI:
     setenv FOAM_MPI eb-mpi
     breaksw
 
 
+# ----
+case sys-mpi:
 case SYSTEMMPI:
     setenv FOAM_MPI sys-mpi
+    setenv WM_MPLIB SYSTEMMPI
     _foamEtc -config prefs.sys-mpi  ## Optional adjustments
 
     # MPI_ARCH_PATH (prefs) or MPI_ROOT (inherited), in that order
@@ -215,8 +243,21 @@ case SYSTEMMPI:
     breaksw
 
 
+# ----
+case mpich:
+case mpich-[1-9]*:
 case MPICH:
+case MPICH-[1-9]*:
     setenv FOAM_MPI mpich-3.3
+
+    ## Add version embedded in the naming
+    set _foamMpiVersion=`echo "$WM_MPLIB" | sed -e 's#[^-]*-##'`
+    if ( "$_foamMpiVersion" != "$WM_MPLIB" ) then
+        setenv FOAM_MPI "mpich-${_foamMpiVersion}"
+        setenv WM_MPLIB "MPICH-${_foamMpiVersion}"
+    else
+        setenv WM_MPLIB MPICH
+    endif
     _foamEtc -config prefs.mpich  ## Optional adjustments
 
     # MPI_ARCH_PATH (prefs) if a valid dir, or use ThirdParty location
@@ -233,6 +274,7 @@ case MPICH:
     breaksw
 
 
+# ----
 case MPICH-GM:
     setenv FOAM_MPI mpich-gm
     _foamEtc -config prefs.mpich-gm  ## Optional adjustments
@@ -253,9 +295,22 @@ case MPICH-GM:
     breaksw
 
 
+# ----
 # MVAPICH2, renamed to contain 'MPI' in its name
+case mvapich2:
+case mvapich2-[1-9]*:
 case MVA2MPI:
+case MVA2MPI-[1-9]*:
     setenv FOAM_MPI mvapich2-2.3
+
+    ## Add version embedded in the naming
+    set _foamMpiVersion=`echo "$WM_MPLIB" | sed -e 's#[^-]*-##'`
+    if ( "$_foamMpiVersion" != "$WM_MPLIB" ) then
+        setenv FOAM_MPI "mvapich2-${_foamMpiVersion}"
+        setenv WM_MPLIB "MVA2MPI-${_foamMpiVersion}"
+    else
+        setenv WM_MPLIB MVA2MPI
+    endif
     _foamEtc -config prefs.mvapich2  ## Optional adjustments
 
     # MPI_ARCH_PATH (prefs) if a valid dir, or ThirdParty location
@@ -271,6 +326,7 @@ case MVA2MPI:
     breaksw
 
 
+# ----
 case CRAY-MPICH:
     setenv FOAM_MPI cray-mpich
     if ( ! $?MPICH_DIR ) setenv MPICH_DIR /dummy
@@ -289,6 +345,7 @@ case CRAY-MPICH:
     breaksw
 
 
+# ----
 case HPMPI:
     setenv FOAM_MPI hpmpi
     setenv MPI_HOME /opt/hpmpi
@@ -317,12 +374,14 @@ case HPMPI:
     breaksw
 
 
+# ----
 case MPI:
     setenv FOAM_MPI mpi
     setenv MPI_ARCH_PATH /opt/mpi
     breaksw
 
 
+# ----
 case FJMPI:
     setenv FOAM_MPI fjmpi
     _foamEtc -config prefs.fjmpi  ## Optional adjustments
@@ -346,6 +405,7 @@ case FJMPI:
     breaksw
 
 
+# ----
 case QSMPI:
     setenv FOAM_MPI qsmpi
     setenv MPI_ARCH_PATH /usr/lib/mpi
@@ -355,6 +415,7 @@ case QSMPI:
     breaksw
 
 
+# ----
 case SGIMPI:
     if ( ! $?MPI_ROOT ) setenv MPI_ROOT /dummy
     if ( "${MPI_ROOT:h}/" == "$MPI_ROOT" ) then
@@ -375,8 +436,22 @@ case SGIMPI:
     breaksw
 
 
-case INTELMPI*:
+# ----
+case intelmpi:
+case intelmpi-[1-9]*:
+case INTELMPI:
+case INTELMPI-[1-9]*:
     setenv FOAM_MPI intelmpi
+
+    ## Add version embedded in the naming
+    set _foamMpiVersion=`echo "$WM_MPLIB" | sed -e 's#[^-]*-##'`
+    if ( "$_foamMpiVersion" != "$WM_MPLIB" ) then
+        setenv FOAM_MPI "intelmpi-${_foamMpiVersion}"
+        setenv WM_MPLIB "INTELMPI-${_foamMpiVersion}"
+    else
+        setenv WM_MPLIB INTELMPI
+        set _foamMpiVersion=latest   ## Fallback value
+    endif
     _foamEtc -config prefs.intelmpi  ## Optional adjustments
 
     if ( $?I_MPI_ROOT ) then
@@ -389,10 +464,14 @@ case INTELMPI*:
         # MPI_ARCH_PATH: Set I_MPI_ROOT accordingly
         setenv I_MPI_ROOT "$MPI_ARCH_PATH"
     else
-        # Final effort - check ThirdParty opt/intel locations for 'latest'
+        # Final effort - check ThirdParty opt/intel locations,
+        # default is 'latest' unless otherwise specified
+
+        if ( "$_foamMpiVersion" == "" ) set _foamMpiVersion=latest
+
         foreach _foamFoundDir (\
-            "$WM_THIRD_PARTY_DIR/opt/intel/oneapi/mpi/latest" \
-            "$WM_THIRD_PARTY_DIR/opt/intel/mpi/latest" \
+            "$WM_THIRD_PARTY_DIR/opt/intel/oneapi/mpi/$_foamMpiVersion" \
+            "$WM_THIRD_PARTY_DIR/opt/intel/mpi/$_foamMpiVersion" \
         )
             if ( -d "$_foamFoundDir" ) then
                 setenv MPI_ARCH_PATH "$_foamFoundDir"
@@ -444,8 +523,21 @@ case INTELMPI*:
     breaksw
 
 
+# ----
+case msmpi:
+case msmpi-[1-9]*:
 case MSMPI:
+case MSMPI-[1-9]*:
     setenv FOAM_MPI msmpi
+
+    ## Add version embedded in the naming
+    set _foamMpiVersion=`echo "$WM_MPLIB" | sed -e 's#[^-]*-##'`
+    if ( "$_foamMpiVersion" != "$WM_MPLIB" ) then
+        setenv FOAM_MPI "msmpi-${_foamMpiVersion}"
+        setenv WM_MPLIB "MSMPI-${_foamMpiVersion}"
+    else
+        setenv WM_MPLIB MSMPI
+    endif
     _foamEtc -config prefs.msmpi  ## Optional adjustments
 
     # MPI_ARCH_PATH (prefs) if a valid dir, or ThirdParty location
@@ -473,13 +565,21 @@ endsw
 
 
 #------------------------------------------------------------------------------
+# Final
+
+# Define fallback value for no MPI
+if ( ! $?FOAM_MPI ) then
+    setenv FOAM_MPI dummy
+else if ( "$FOAM_MPI" == "" ) then
+    setenv FOAM_MPI dummy
+endif
 
 # Report
 if ($?FOAM_VERBOSE && $?prompt) then
     echo "Using mpi type : $WM_MPLIB"
     echo "      FOAM_MPI : $FOAM_MPI"
     if ( "${MPI_ARCH_PATH}" == "" ) then
-        echo "        prefix : unset"
+        echo "        prefix : []"
     else
         echo "        prefix : $MPI_ARCH_PATH"
     endif
diff --git a/etc/config.csh/unset b/etc/config.csh/unset
index b9a611ddc1..0d531b5082 100644
--- a/etc/config.csh/unset
+++ b/etc/config.csh/unset
@@ -116,7 +116,14 @@ unsetenv FOAM_INST_DIR
 
 unsetenv MPI_ARCH_PATH
 unsetenv MPI_BUFFER_SIZE
-unsetenv OPAL_PREFIX
+
+# Cleanup mpi prefix values if set to one of the paths on foamOldDirs
+if ( $?foamClean ) then
+    # openmpi:
+    if ( "`$foamClean -env=OPAL_PREFIX $foamOldDirs`" == "" ) unsetenv OPAL_PREFIX
+    # intelmpi:
+    if ( "`$foamClean -env=I_MPI_ROOT $foamOldDirs`" == "" ) unsetenv I_MPI_ROOT
+endif
 
 
 #------------------------------------------------------------------------------
@@ -175,6 +182,8 @@ if ($?DYLD_LIBRARY_PATH) then
     if ("${DYLD_LIBRARY_PATH}" == "") unsetenv DYLD_LIBRARY_PATH
 endif
 
+# Remove any shadow env variables
+unsetenv FOAM_DYLD_LIBRARY_PATH
 
 #------------------------------------------------------------------------------
 # Cleanup aliases
@@ -221,6 +230,6 @@ endif
 #------------------------------------------------------------------------------
 # Intermediate variables (do as last for a clean exit code)
 
-unset cleaned foamClean foamOldDirs
+unset cleaned foamClean foamOldDirs _foamFoundDir
 
 #------------------------------------------------------------------------------
diff --git a/etc/config.sh/functions b/etc/config.sh/functions
index 105ca2d4c5..d3765d29ac 100644
--- a/etc/config.sh/functions
+++ b/etc/config.sh/functions
@@ -29,7 +29,7 @@
 #     _foamClean     : eval call to foamCleanPath for specific shell
 #     _foamEcho      : silent/non-silent echo
 #     _foamEtc       : resolve etc files (silent or verbose)
-#     _foamAddPath   : prepend to MANPATH
+#     _foamAddPath   : prepend to PATH
 #     _foamAddMan    : prepend to MANPATH
 #     _foamAddLib    : prepend to [DY]LD_LIBRARY_PATH
 #     _foamAddLibAuto: prepend to lib64/lib resolved name
diff --git a/etc/config.sh/mpi b/etc/config.sh/mpi
index 1e056c3ec9..5310a6c293 100644
--- a/etc/config.sh/mpi
+++ b/etc/config.sh/mpi
@@ -46,29 +46,49 @@
 #------------------------------------------------------------------------------
 unset MPI_ARCH_PATH MPI_HOME
 export FOAM_MPI=dummy  # Fallback value
-unset _foamMpiVersion  # Track mpi (major) version as required
+unset _foamMpiVersion  # Track mpi version as required
 
 # Location for ThirdParty installations
 _foamMpiPrefixDir="$WM_THIRD_PARTY_DIR/platforms/$WM_ARCH$WM_COMPILER"
 _foamMpiWarning="openfoam (etc/config.sh/mpi) => "  # Prefix for warnings
 
+# Version embedded in the naming
+# $1 = mpi family (eg, openmpi, mpich, ...)
+# Eg, _foamMpiEmbedVersion openmpi OPENMPI
+unset -f _foamMpiEmbedVersion 2>/dev/null
+_foamMpiEmbedVersion()
+{
+    # Version embedded in the naming. Eg, OPENMPI-4.0.3
+    _foamMpiVersion="${WM_MPLIB#*-}"
+    if [ -n "$_foamMpiVersion" ] && [ "$_foamMpiVersion" != "$WM_MPLIB" ]
+    then
+        [ -n "$1" ] && FOAM_MPI="${1}-${_foamMpiVersion}"
+        [ -n "$2" ] && WM_MPLIB="${2}-${_foamMpiVersion}"
+    else
+        [ -n "$2" ] && WM_MPLIB="${2}"
+        unset _foamMpiVersion  # Extra safety
+    fi
+}
+
+
 #------------------------------------------------------------------------------
 
 case "$WM_MPLIB" in
 
-# The system openmpi, discover locations via <mpicc>
-# Preserve major version for the naming
-SYSTEMOPENMPI | SYSTEMOPENMPI[1-9])
-    # Preserve major version for the naming
+# ----
+# The system openmpi, discover locations by orte-info, mpicc or orterun
+# Preserve major or full version for the naming
+sys-openmpi | sys-openmpi[1-9] | sys-openmpi-[1-9]* |\
+SYSTEMOPENMPI | SYSTEMOPENMPI[1-9] | SYSTEMOPENMPI-[1-9]*)
+    # Preserve version or full version for the naming
     _foamMpiVersion="${WM_MPLIB##*MPI}"
+    _foamMpiVersion="${_foamMpiVersion##*mpi}"
 
     export FOAM_MPI="sys-openmpi${_foamMpiVersion}"
+    export WM_MPLIB="SYSTEMOPENMPI${_foamMpiVersion}"
 
     # Undefine OPAL_PREFIX if set to one of the paths on foamOldDirs
-    if [ -z "$($foamClean -env=OPAL_PREFIX "$foamOldDirs")" ]
-    then
-        unset OPAL_PREFIX
-    fi
+    [ -z "$($foamClean -env=OPAL_PREFIX "$foamOldDirs")" ] && unset OPAL_PREFIX
     _foamEtc -config prefs.sys-openmpi  ## Optional adjustments
 
     unset _foamFoundCmd
@@ -76,6 +96,7 @@ SYSTEMOPENMPI | SYSTEMOPENMPI[1-9])
     # MPI_ARCH_PATH (prefs) if a valid dir, or need to discover
     if [ -d "$MPI_ARCH_PATH" ]
     then
+        _foamAddPath    "$MPI_ARCH_PATH"/bin
         _foamAddLibAuto "$MPI_ARCH_PATH"
     else
         unset MPI_ARCH_PATH
@@ -145,8 +166,12 @@ SYSTEMOPENMPI | SYSTEMOPENMPI[1-9])
     ;;
 
 
-OPENMPI)
+# ----
+openmpi | openmpi-[1-9]* |\
+OPENMPI | OPENMPI-[1-9]* )
     export FOAM_MPI=openmpi-4.0.3
+
+    _foamMpiEmbedVersion openmpi OPENMPI
     _foamEtc -config prefs.openmpi  ## Optional adjustments
 
     # MPI_ARCH_PATH (prefs) if a valid dir, or ThirdParty location
@@ -168,6 +193,7 @@ OPENMPI)
     ;;
 
 
+# ----
 # Arbitrary, user-specified mpi implementation
 # - used by spack, which populates appropriate wmake rules
 USERMPI)
@@ -176,14 +202,19 @@ USERMPI)
     ;;
 
 
+# ----
 # EasyBuild handles everything via <mpicc>
 EASYBUILDMPI)
     export FOAM_MPI=eb-mpi
     ;;
 
 
+# ----
+sys-mpi |\
 SYSTEMMPI)
     export FOAM_MPI=sys-mpi
+    export WM_MPLIB=SYSTEMMPI
+
     _foamEtc -config prefs.sys-mpi  ## Optional adjustments
 
     # MPI_ARCH_PATH (prefs) or MPI_ROOT (inherited), in that order
@@ -230,8 +261,12 @@ SYSTEMMPI)
     ;;
 
 
-MPICH)
+# ----
+mpich | mpich-[1-9]* |\
+MPICH | MPICH-[1-9]* )
     export FOAM_MPI=mpich-3.3
+
+    _foamMpiEmbedVersion mpich MPICH
     _foamEtc -config prefs.mpich  ## Optional adjustments
 
     # MPI_ARCH_PATH (prefs) if a valid dir, or use ThirdParty location
@@ -252,6 +287,7 @@ MPICH)
     ;;
 
 
+# ----
 MPICH-GM)
     export FOAM_MPI=mpich-gm
     _foamEtc -config prefs.mpich-gm  ## Optional adjustments
@@ -274,9 +310,13 @@ MPICH-GM)
     ;;
 
 
+# ----
 # MVAPICH2, renamed to contain 'MPI' in its name
-MVA2MPI)
+mvapich2 | mvapich2-[1-9]* |\
+MVA2MPI | MVA2MPI-[1-9]* )
     export FOAM_MPI=mvapich2-2.3
+
+    _foamMpiEmbedVersion mvapich2 MVA2MPI
     _foamEtc -config prefs.mvapich2  ## Optional adjustments
 
     # MPI_ARCH_PATH (prefs) if a valid dir, or ThirdParty location
@@ -295,6 +335,7 @@ MVA2MPI)
     ;;
 
 
+# ----
 CRAY-MPICH)
     export FOAM_MPI=cray-mpich
     export MPI_ARCH_PATH="$MPICH_DIR"
@@ -313,6 +354,7 @@ CRAY-MPICH)
     ;;
 
 
+# ----
 HPMPI)
     export FOAM_MPI=hpmpi
     export MPI_HOME=/opt/hpmpi
@@ -336,12 +378,14 @@ HPMPI)
     ;;
 
 
+# ----
 MPI)
     export FOAM_MPI=mpi
     export MPI_ARCH_PATH=/opt/mpi
     ;;
 
 
+# ----
 FJMPI)
     export FOAM_MPI=fjmpi
     _foamEtc -config prefs.fjmpi  ## Optional adjustments
@@ -368,6 +412,7 @@ FJMPI)
     ;;
 
 
+# ----
 QSMPI)
     export FOAM_MPI=qsmpi
     export MPI_ARCH_PATH=/usr/lib/mpi
@@ -377,6 +422,7 @@ QSMPI)
     ;;
 
 
+# ----
 SGIMPI)
     : "${MPI_ROOT:=/dummy}"
     MPI_ROOT="${MPI_ROOT%/}" # Remove trailing slash
@@ -395,8 +441,15 @@ SGIMPI)
     ;;
 
 
-INTELMPI*)
+# ----
+intelmpi | intelmpi-[1-9]* |\
+INTELMPI | INTELMPI-[1-9]* )
     export FOAM_MPI=intelmpi
+
+    _foamMpiEmbedVersion intelmpi INTELMPI
+
+    # Undefine I_MPI_ROOT if set to one of the paths on foamOldDirs
+    [ -z "$($foamClean -env=I_MPI_ROOT "$foamOldDirs")" ] && unset I_MPI_ROOT
     _foamEtc -config prefs.intelmpi  ## Optional adjustments
 
     if [ -n "$I_MPI_ROOT" ]
@@ -415,10 +468,14 @@ INTELMPI*)
         export I_MPI_ROOT="$MPI_ARCH_PATH"
 
     else
-        # Final effort - check ThirdParty opt/intel locations for 'latest'
+        # Final effort - check ThirdParty opt/intel locations,
+        # default is 'latest' unless otherwise specified
+
+        [ -n "${_foamMpiVersion}" ] || _foamMpiVersion=latest
+
         for _foamFoundDir in \
-            "$WM_THIRD_PARTY_DIR/opt/intel/oneapi/mpi/latest" \
-            "$WM_THIRD_PARTY_DIR/opt/intel/mpi/latest" \
+            "$WM_THIRD_PARTY_DIR/opt/intel/oneapi/mpi/$_foamMpiVersion" \
+            "$WM_THIRD_PARTY_DIR/opt/intel/mpi/$_foamMpiVersion" \
         ;
         do
             if [ -d "$_foamFoundDir" ]
@@ -478,8 +535,12 @@ INTELMPI*)
     ;;
 
 
-MSMPI)
+# ----
+msmpi | msmpi-[1-9]* |\
+MSMPI | MSMPI-[1-9]* )
     export FOAM_MPI=msmpi
+
+    _foamMpiEmbedVersion msmpi MSMPI
     _foamEtc -config prefs.msmpi  ## Optional adjustments
 
     # MPI_ARCH_PATH (prefs) if a valid dir, or ThirdParty location
@@ -513,6 +574,9 @@ esac
 #------------------------------------------------------------------------------
 # Final
 
+: "${FOAM_MPI:=dummy}"  # Fallback value for no MPI
+export FOAM_MPI
+
 # Ensure MPI_ARCH_PATH is marked for export
 [ -n "$MPI_ARCH_PATH" ] && export MPI_ARCH_PATH
 
@@ -521,10 +585,11 @@ if [ -n "$FOAM_VERBOSE" ] && [ -n "$PS1" ]
 then
     echo "Using mpi type : $WM_MPLIB" 1>&2
     echo "      FOAM_MPI : $FOAM_MPI" 1>&2
-    echo "        prefix : ${MPI_ARCH_PATH:-[unset]}" 1>&2
+    echo "        prefix : ${MPI_ARCH_PATH:-[]}" 1>&2
 fi
 
 # Cleanup
 unset _foamMpiPrefixDir _foamMpiVersion _foamMpiWarning
+unset -f _foamMpiEmbedVersion 2>/dev/null
 
 #------------------------------------------------------------------------------
diff --git a/etc/config.sh/unset b/etc/config.sh/unset
index ec50b9753a..6ed8599394 100644
--- a/etc/config.sh/unset
+++ b/etc/config.sh/unset
@@ -106,10 +106,13 @@ unset FOAM_INST_DIR
 unset MPI_ARCH_PATH
 unset MPI_BUFFER_SIZE
 
-# Undefine OPAL_PREFIX if set to one of the paths on foamOldDirs
-if [ -n "$foamClean" ] && [ -z "$($foamClean -env=OPAL_PREFIX $foamOldDirs)" ]
+# Cleanup mpi prefix values if set to one of the paths on foamOldDirs
+if [ -n "$foamClean" ]
 then
-    unset OPAL_PREFIX
+    # openmpi:
+    [ -z "$($foamClean -env=OPAL_PREFIX $foamOldDirs)" ] && unset OPAL_PREFIX
+    # intelmpi:
+    [ -z "$($foamClean -env=I_MPI_ROOT $foamOldDirs)" ] && unset I_MPI_ROOT
 fi
 
 #------------------------------------------------------------------------------
@@ -163,6 +166,9 @@ fi
 [ -n "$LD_LIBRARY_PATH" ] || unset LD_LIBRARY_PATH
 [ -n "$DYLD_LIBRARY_PATH" ] || unset DYLD_LIBRARY_PATH
 
+# Remove any shadow env variables
+unset FOAM_DYLD_LIBRARY_PATH
+
 #------------------------------------------------------------------------------
 # Cleanup aliases and functions
 
@@ -220,6 +226,6 @@ unset _of_complete_cache_
 #------------------------------------------------------------------------------
 # Intermediate variables (do as last for a clean exit code)
 
-unset cleaned foamClean foamOldDirs
+unset cleaned foamClean foamOldDirs _foamFoundDir
 
 #------------------------------------------------------------------------------
diff --git a/wmake/rules/General/mpi-rules b/wmake/rules/General/mpi-rules
index cfcd6d6eca..411e0f7f5c 100644
--- a/wmake/rules/General/mpi-rules
+++ b/wmake/rules/General/mpi-rules
@@ -5,20 +5,27 @@ PFLAGS  =
 PINC    =
 PLIBS   =
 
-# The stem name. Eg, SYSTEMOPENMPI4 -> SYSTEMOPENMPI
-MPLIB_STEMNAME = $(shell echo "$(WM_MPLIB)" | sed -e 's/[-.0-9]*$$//')
+# Extract the family name. For example,
+# SYSTEMOPENMPI4 -> SYSTEMOPENMPI
+# OPENMPI-4.0.6 -> OPENMPI
+#
+MPLIB_FAMILY = $(shell echo "$(WM_MPLIB)" | sed -e 's/[-+.0-9~].*//')
 
-ifneq ("$(MPLIB_STEMNAME)","$(WM_MPLIB)")
-    sinclude $(GENERAL_RULES)/mplib$(MPLIB_STEMNAME)
-    sinclude $(DEFAULT_RULES)/mplib$(MPLIB_STEMNAME)
+# Base rules
+ifneq ("$(MPLIB_FAMILY)","$(WM_MPLIB)")
+    sinclude $(GENERAL_RULES)/mplib$(MPLIB_FAMILY)
+    sinclude $(DEFAULT_RULES)/mplib$(MPLIB_FAMILY)
+    # system-specific
     ifneq ("$(RULES)","$(DEFAULT_RULES)")
-        sinclude $(RULES)/mplib$(MPLIB_STEMNAME)
+        sinclude $(RULES)/mplib$(MPLIB_FAMILY)
     endif
 endif
 
+# Specific rules
 ifneq ("","$(WM_MPLIB)")
     sinclude $(GENERAL_RULES)/mplib$(WM_MPLIB)
     sinclude $(DEFAULT_RULES)/mplib$(WM_MPLIB)
+    # system-specific
     ifneq ("$(RULES)","$(DEFAULT_RULES)")
         sinclude $(RULES)/mplib$(WM_MPLIB)
     endif