diff --git a/EESSI-install-software.sh b/EESSI-install-software.sh
index a2442e0d..a6f34413 100755
--- a/EESSI-install-software.sh
+++ b/EESSI-install-software.sh
@@ -134,7 +134,7 @@ if [[ "${EESSI_INTERACTIVE_BUILD}" == "onfail" ]]; then
 fi
 
 # honor $TMPDIR if it is already defined, use /tmp otherwise
-if [ -z $TMPDIR ]; then
+if [[ -z $TMPDIR ]]; then
     export WORKDIR=/tmp/$USER
 else
     export WORKDIR=$TMPDIR/$USER
@@ -155,7 +155,7 @@ if [[ "$EASYBUILD_OPTARCH" == "GENERIC" ]]; then
 fi
 
 echo ">> Determining software subdirectory to use for current build host..."
-if [ -z $EESSI_SOFTWARE_SUBDIR_OVERRIDE ]; then
+if [[ -z $EESSI_SOFTWARE_SUBDIR_OVERRIDE ]]; then
   export EESSI_SOFTWARE_SUBDIR_OVERRIDE=$(python3 $TOPDIR/eessi_software_subdir.py $DETECTION_PARAMETERS)
   echo ">> Determined \$EESSI_SOFTWARE_SUBDIR_OVERRIDE via 'eessi_software_subdir.py $DETECTION_PARAMETERS' script"
 else
@@ -173,18 +173,30 @@ else
 
       # make sure the the software and modules directory exist
       # (since it's expected by init/eessi_environment_variables when using archdetect and by the EESSI module)
-      mkdir -p -v ${EESSI_PREFIX}/software/${EESSI_OS_TYPE}/${EESSI_SOFTWARE_SUBDIR_OVERRIDE}/{modules,software}
+      if [[ ! -z "${EESSI_SITE_INSTALL_FORCE}" ]]; then
+          if [[ ! -z "${EESSI_SITE_SOFTWARE_PREFIX}" ]]; then
+              mkdir -p -v ${EESSI_SITE_SOFTWARE_PREFIX}/versions/${EESSI_VERSION_OVERRIDE:-${EESSI_VERSION}}/software/${EESSI_OS_TYPE}/${EESSI_SOFTWARE_SUBDIR_OVERRIDE}/{modules,software}
+          else
+              fatal_error 'Requested a site installation, but $EESSI_SITE_SOFTWARE_PREFIX is somehow not set?! This should have been set by bot/build.sh.'
+          fi
+      else
+          mkdir -p -v ${EESSI_PREFIX}/software/${EESSI_OS_TYPE}/${EESSI_SOFTWARE_SUBDIR_OVERRIDE}/{modules,software}
+      fi
 
       # If EESSI_ACCELERATOR_TARGET_OVERRIDE is defined, we are building for an accelerator target
       # In that case, make sure the modulepath for the accelerator subdir exists, otherwise the EESSI module will not
       # set EESSI_ACCELERATOR_TARGET and the if-condition later in this script which checks if EESSI_ACCELERATOR_TARGET
       # is equal to EESSI_ACCELERATOR_TARGET_OVERRIDE will fail 
       # See https://github.com/EESSI/software-layer-scripts/pull/59#issuecomment-3173593882
-      if [ -n $EESSI_ACCELERATOR_TARGET_OVERRIDE ]; then
+      if [[ -n $EESSI_ACCELERATOR_TARGET_OVERRIDE ]]; then
           # Note that ${EESSI_PREFIX}/software/${EESSI_OS_TYPE}/${EESSI_SOFTWARE_SUBDIR_OVERRIDE}/${EESSI_ACCELERATOR_TARGET_OVERRIDE}/modules/all
           # is only the correct path if EESSI_ACCEL_SOFTWARE_SUBDIR_OVERRIDE is not set
-          if [ -z $EESSI_ACCEL_SOFTWARE_SUBDIR_OVERRIDE ]; then
-              mkdir -p -v ${EESSI_PREFIX}/software/${EESSI_OS_TYPE}/${EESSI_SOFTWARE_SUBDIR_OVERRIDE}/${EESSI_ACCELERATOR_TARGET_OVERRIDE}/modules/all
+          if [[ -z $EESSI_ACCEL_SOFTWARE_SUBDIR_OVERRIDE ]]; then
+              if [[ ! -z "${EESSI_SITE_INSTALL_FORCE}" ]]; then
+                  mkdir -p -v ${EESSI_SITE_SOFTWARE_PREFIX}/versions/${EESSI_VERSION_OVERRIDE:-${EESSI_VERSION}}/software/${EESSI_OS_TYPE}/${EESSI_SOFTWARE_SUBDIR_OVERRIDE}/${EESSI_ACCELERATOR_TARGET_OVERRIDE}/modules/all
+              else
+                  mkdir -p -v ${EESSI_PREFIX}/software/${EESSI_OS_TYPE}/${EESSI_SOFTWARE_SUBDIR_OVERRIDE}/${EESSI_ACCELERATOR_TARGET_OVERRIDE}/modules/all
+              fi
           else
               # At runtime, one might want to use a different CPU subdir for a given accelerator. E.g. one could use
               # a zen2 CPU subdir on a zen4 node if the required GPU software isn't available in the zen4 tree.
@@ -203,7 +215,7 @@ fi
 echo ">> Setting up environment..."
 
 # If EESSI_VERSION is not set, source the defaults script to set it
-if [ -z ${EESSI_VERSION} ]; then
+if [[ -z ${EESSI_VERSION} ]]; then
     source $TOPDIR/init/eessi_defaults
 fi
 
@@ -261,13 +273,13 @@ else
     fatal_error "Not running in Gentoo Prefix environment, run '${EPREFIX}/startprefix' first!"
 fi
 
-if [ -d $EESSI_CVMFS_REPO ]; then
+if [[ -d $EESSI_CVMFS_REPO ]]; then
     echo_green "$EESSI_CVMFS_REPO available, OK!"
 else
     fatal_error "$EESSI_CVMFS_REPO is not available!"
 fi
 if [[ -n "$EESSI_CVMFS_REPO_OVERRIDE" && "$EESSI_CVMFS_REPO" != "$EESSI_CVMFS_REPO_OVERRIDE" ]]; then
-    if [ -d "$EESSI_CVMFS_REPO_OVERRIDE" ]; then
+    if [[ -d "$EESSI_CVMFS_REPO_OVERRIDE" ]]; then
         echo_green "$EESSI_CVMFS_REPO_OVERRIDE available, OK!"
     else
         fatal_error "$EESSI_CVMFS_REPO_OVERRIDE is not available!"
@@ -294,13 +306,14 @@ export PYTHONUNBUFFERED=1
 # - .lmod/lmodrc.lua
 # - .lmod/SitePackage.lua
 if [[ -n "${EESSI_SITE_INSTALL_FORCE}" ]]; then
-    _eessi_software_path=${EESSI_CVMFS_REPO_OVERRIDE}/versions/${EESSI_VERSION_OVERRIDE:-${EESSI_VERSION}}/software/${EESSI_OS_TYPE}/${EESSI_SOFTWARE_SUBDIR_OVERRIDE}
+    # note: we need to use EESSI_SITE_SOFTWARE_PREFIX_BACKUP here, as we have temporarily unset EESSI_SITE_SOFTWARE_PREFIX above
+    _eessi_software_path=${EESSI_SITE_SOFTWARE_PREFIX_BACKUP}/versions/${EESSI_VERSION_OVERRIDE:-${EESSI_VERSION}}/software/${EESSI_OS_TYPE}/${EESSI_SOFTWARE_SUBDIR_OVERRIDE}
 else
     _eessi_software_path=${EESSI_PREFIX}/software/${EESSI_OS_TYPE}/${EESSI_SOFTWARE_SUBDIR_OVERRIDE}
 fi
 _lmod_cfg_dir=${_eessi_software_path}/.lmod
 _lmod_rc_file=${_lmod_cfg_dir}/lmodrc.lua
-if [ ! -f ${_lmod_rc_file} ]; then
+if [[ ! -f ${_lmod_rc_file} ]]; then
     echo "Lmod file '${_lmod_rc_file}' does not exist yet; creating it..."
     command -V python3
     python3 ${TOPDIR}/create_lmodrc.py ${_eessi_software_path}
@@ -371,7 +384,7 @@ temp_install_storage=${TMPDIR}/temp_install_storage
 # Make sure that we use the easystack files from the git repository, which has an additional subdirectory ${EESSI_VERSION} at the end
 export NVIDIA_EASYSTACKS_DIRECTORY=${TOPDIR}/scripts/gpu_support/nvidia/easystacks/${EESSI_VERSION}
 mkdir -p ${temp_install_storage}
-if [ -z "${skip_cuda_install}" ] || [ ! "${skip_cuda_install}" ]; then
+if [[ -z "${skip_cuda_install}" ]] || [[ ! "${skip_cuda_install}" ]]; then
     ${TOPDIR}/scripts/gpu_support/nvidia/install_cuda_and_libraries.sh \
         -t ${temp_install_storage} \
         --accept-cuda-eula \
@@ -402,16 +415,16 @@ if [[ ! -z "${EESSI_SITE_INSTALL}" && ! -z "${EESSI_SITE_SOFTWARE_PREFIX}" ]]; t
     echo "EASYBUILD_INSTALLPATH=${EASYBUILD_INSTALLPATH}"
 fi
 
-if [ ! -z "${shared_fs_path}" ]; then
+if [[ ! -z "${shared_fs_path}" ]]; then
     shared_eb_sourcepath=${shared_fs_path}/easybuild/sources
     echo ">> Using ${shared_eb_sourcepath} as shared EasyBuild source path"
     export EASYBUILD_SOURCEPATH=${shared_eb_sourcepath}:${EASYBUILD_SOURCEPATH}
 fi
 
 # if an accelerator target is specified, we need to make sure that the CPU-only modules are also still available
-if [ ! -z ${EESSI_ACCELERATOR_TARGET} ]; then
+if [[ ! -z ${EESSI_ACCELERATOR_TARGET} ]]; then
     CPU_ONLY_MODULES_PATH=$(echo $EASYBUILD_INSTALLPATH | sed "s@/${EESSI_ACCELERATOR_TARGET}@@g")/modules/all
-    if [ -d ${CPU_ONLY_MODULES_PATH} ]; then
+    if [[ -d ${CPU_ONLY_MODULES_PATH} ]]; then
         module use ${CPU_ONLY_MODULES_PATH}
     else
         fatal_error "Derived path to CPU-only modules does not exist: ${CPU_ONLY_MODULES_PATH}"
@@ -433,7 +446,7 @@ fi
 # Note that we exclude the scripts/gpu_support/ dir, since those are not meant to be built in the
 # software-layer, but they are helper easystacks for installing e.g. CUDA in host_injections
 changed_easystacks=$(cat ${pr_diff} | grep '^+++' | cut -f2 -d' ' | sed 's@^[a-z]/@@g' | grep 'easystacks/.*yml$' | egrep -v 'known-issues|missing' | (grep -v "scripts/gpu_support/" || true)) 
-if [ -z "${changed_easystacks}" ]; then
+if [[ -z "${changed_easystacks}" ]]; then
     echo "No missing installations, party time!"  # Ensure the bot report success, as there was nothing to be build here
 else
 
@@ -453,10 +466,10 @@ else
         # make sure that easystack file being picked up is for EESSI version that we're building for...
         # Preferentially check EESSI_CVMFS_REPO_OVERRIDE (since that is set for site builds), otherwise default to EESSI_CVMFS_REPO
         echo "${easystack_file}" | grep -q "^easystacks/$(basename ${EESSI_CVMFS_REPO_OVERRIDE:-${EESSI_CVMFS_REPO}})/${EESSI_VERSION}${EESSI_SOFTWARE_LAYER_VERSION_SUFFIX}/"
-        if [ $? -ne 0 ]; then
+        if [[ $? -ne 0 ]]; then
             # Check if this was even an easystack file for the right repository
             echo "${easystack_file}" | grep -q "^easystacks/$(basename ${EESSI_CVMFS_REPO_OVERRIDE:-${EESSI_CVMFS_REPO}})"
-            if [ $? -ne 0 ]; then
+            if [[ $? -ne 0 ]]; then
                 echo_yellow "Easystack file ${easystack_file} is not intended for the repository ${EESSI_CVMFS_REPO_OVERRIDE:-${EESSI_CVMFS_REPO}}, skipping it..."
             else
                 echo_yellow "Easystack file ${easystack_file} is not intended for EESSI version ${EESSI_VERSION}${EESSI_SOFTWARE_LAYER_VERSION_SUFFIX}, skipping it..."
@@ -489,14 +502,14 @@ else
                 debug_shell "environment is ready to run: ${eb_cmd}"
             fi
 
-            if [ -f ${easystack_file} ]; then
+            if [[ -f ${easystack_file} ]]; then
                 echo_green "Feeding easystack file ${easystack_file} to EasyBuild..."
 
                 ${eb_cmd}
                 ec=$?
 
                 # copy EasyBuild log file if EasyBuild exited with an error
-                if [ ${ec} -ne 0 ]; then
+                if [[ ${ec} -ne 0 ]]; then
                     # If easybuild had a non-zero exit code, and EESSI_INTERACTIVE_BUILD=onfail, you'll get a debug
                     # shell so you can debug the failure
                     if [[ "${EESSI_INTERACTIVE_BUILD}" == "onfail" ]]; then
@@ -504,7 +517,7 @@ else
                     fi
                     eb_last_log=$(eb --last-log | grep ^/.*\.log)
                     # copy to current working directory if file exhists
-                    if [ -f ${eb_last_log} ]; then
+                    if [[ -f ${eb_last_log} ]]; then
                         cp -a ${eb_last_log} .
                         echo "Last EasyBuild log file copied from ${eb_last_log} to ${PWD}"
                         # copy to build logs dir (with context added)
@@ -538,7 +551,7 @@ if [[ -z "${EESSI_SITE_INSTALL}" ]]; then
         echo "Path to lmodrc.lua changed to '${lmod_rc_file}'"
     fi
     lmodrc_changed=$(cat ${pr_diff} | grep '^+++' | cut -f2 -d' ' | sed 's@^[a-z]/@@g' | grep '^create_lmodrc.py$' > /dev/null; echo $?)
-    if [ ! -f $lmod_rc_file ] || [ ${lmodrc_changed} == '0' ]; then
+    if [[ ! -f $lmod_rc_file ]] || [[ ${lmodrc_changed} == '0' ]]; then
         echo ">> Creating/updating Lmod RC file (${lmod_rc_file})..."
         python3 $TOPDIR/create_lmodrc.py ${EASYBUILD_INSTALLPATH}
         check_exit_code $? "$lmod_rc_file created" "Failed to create $lmod_rc_file"
@@ -548,7 +561,7 @@ else
     # The only way to then trigger a redeploy is if we do something like
     # python3 $TOPDIR/create_lmodrc.py $TMDPIR
     # foo=$(diff $lmod_rc_file $TMPDIR/.lmod/lmodrc.lua)
-    # if [ -z $foo ]; then
+    # if [[ -z $foo ]]; then
     #     python3 $TOPDIR/create_lmodrc.py ${EASYBUILD_INSTALLPATH}
     # fi
     # in order to detect if our deployed lmodrc.lua is different from the one that _would_ be newly generated
@@ -565,7 +578,7 @@ if [[ -z "${EESSI_SITE_INSTALL}" ]]; then
         echo "Path to SitePackage.lua changed to '${lmod_sitepackage_file}'"
     fi
     sitepackage_changed=$(cat ${pr_diff} | grep '^+++' | cut -f2 -d' ' | sed 's@^[a-z]/@@g' | grep '^create_lmodsitepackage.py$' > /dev/null; echo $?)
-    if [ ! -f "$lmod_sitepackage_file" ] || [ "${sitepackage_changed}" == '0' ]; then
+    if [[ ! -f "$lmod_sitepackage_file" ]] || [[ "${sitepackage_changed}" == '0' ]]; then
         echo ">> Creating/updating Lmod SitePackage.lua (${lmod_sitepackage_file})..."
         python3 $TOPDIR/create_lmodsitepackage.py ${EASYBUILD_INSTALLPATH}
         check_exit_code $? "$lmod_sitepackage_file created" "Failed to create $lmod_sitepackage_file"