diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 2d26d33d..3375996c 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -14,10 +14,13 @@ jobs:
     strategy:
       matrix:
         include:
-          #- {os: macOS-latest}
-          - {os: ubuntu-latest}
+          - { name: container, os: ubuntu-latest, container: rocker/r2u4ci }
+          - { name: macos,     os: macos-latest }
+          #- { name: ubuntu,    os: ubuntu-latest }
+
 
     runs-on: ${{ matrix.os }}
+    container: ${{ matrix.container }}
 
     steps:
       - name: Checkout
@@ -25,6 +28,11 @@ jobs:
 
       - name: Setup
         uses: eddelbuettel/github-actions/r-ci@master
+        with:
+          dev_version: 'TRUE'
+
+      - name: Configure
+        run: ./configure; cat src/Makevars
 
       - name: Dependencies
         run: ./run.sh install_deps
diff --git a/ChangeLog b/ChangeLog
index ab86ac72..9e3121c7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -7,6 +7,11 @@
 
 	* inst/include/current/: Sync with Armadillo 15.2
 
+2025-10-18  Dirk Eddelbuettel  <edd@debian.org>
+
+	* configure.ac: Simplified OpenMP setup
+	* configure: Idem
+
 2025-10-17  Dirk Eddelbuettel  <edd@debian.org>
 
 	* src/RcppArmadillo.cpp (armadillo_version_typed): Added
diff --git a/configure b/configure
index 4f0e79c6..b85f34b2 100755
--- a/configure
+++ b/configure
@@ -3227,11 +3227,11 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
 
 ## Is R already configured to compile things using OpenMP without
 ## any extra hand-holding?
-openmp_already_works="no"
+#openmp_already_works="no"
 
 ## default to not even thinking about OpenMP as Armadillo wants a pragma
 ## variant available if and only if C++11 is used with g++ 5.4 or newer
-can_use_openmp="no"
+#can_use_openmp="no"
 
 ## Ensure TMPDIR is set.
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether we have a suitable tempdir" >&5
@@ -3264,154 +3264,40 @@ if test x"$?" = x"0"; then
     { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: yes" >&5
 printf "%s\n" "yes" >&6; }
     openmp_already_works="yes"
+    arma_have_openmp="#define ARMA_USE_OPENMP 1"
+    can_use_openmp="yes"
 else
     { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
 printf "%s\n" "no" >&6; }
+    openmp_already_works="no"
+    arma_have_openmp="#define ARMA_DONT_USE_OPENMP 1"
+    can_use_openmp="no"
 fi
 
 ## Go back home.
 cd "${owd}"
 rm -rf "${BUILDDIR}"
 
-## If the above checks failed, then perform other heuristics
-## based on the compiler version, etc.
-if test x"${openmp_already_works}" = x"no"; then
-
-    ## Check the C++ compiler using the CXX value set
-
-    ## If it is g++, we have GXX set so let's examine it
-    if test "${GXX}" = yes; then
-        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether g++ version is sufficient" >&5
-printf %s "checking whether g++ version is sufficient... " >&6; }
-        gxx_version=$(${CXX} -v 2>&1 | awk '/^.*g.. version/ {print $3}')
-        case ${gxx_version} in
-            1.*|2.*|3.*|4.0.*|4.1.*|4.2.*|4.3.*|4.4.*|4.5.*|4.6.*|4.7.0|4.7.1)
-                 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
-printf "%s\n" "no" >&6; }
-                 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: Only g++ version 4.7.2 or greater can be used with RcppArmadillo." >&5
-printf "%s\n" "$as_me: WARNING: Only g++ version 4.7.2 or greater can be used with RcppArmadillo." >&2;}
-                 as_fn_error $? "Please use a different compiler." "$LINENO" 5
-            ;;
-            4.7.*|4.8.*|4.9.*|5.0*|5.1*|5.2*|5.3*)
-                 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: yes, but without OpenMP as version ${gxx_version} (Armadillo constraint)" >&5
-printf "%s\n" "yes, but without OpenMP as version ${gxx_version} (Armadillo constraint)" >&6; }
-                 ## we know this one is bad
-                 can_use_openmp="no"
-            ;;
-            5.4*|5.5*|5.6*|5.7*|5.8*|5.9*|6.*|7.*|8.*|9.*|1?.*)
-                 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: yes, with OpenMP as version ${gxx_version}" >&5
-printf "%s\n" "yes, with OpenMP as version ${gxx_version}" >&6; }
-                 ## we know this one is good, yay
-                 can_use_openmp="yes"
-            ;;
-            *)
-                 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: almost" >&5
-printf "%s\n" "almost" >&6; }
-                 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: Compiler self-identifies as being compliant with GNUC extensions but is not g++." >&5
-printf "%s\n" "$as_me: WARNING: Compiler self-identifies as being compliant with GNUC extensions but is not g++." >&2;}
-                 ## we know nothing, so no
-                 can_use_openmp="no"
-            ;;
-        esac
-    fi
-
-    ## Check for Apple LLVM
-
-    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for macOS" >&5
+## Additional Apple check
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for macOS" >&5
 printf %s "checking for macOS... " >&6; }
-    RSysinfoName=$("${R_HOME}/bin/Rscript" --vanilla -e 'cat(Sys.info()["sysname"])')
-
-    if test x"${RSysinfoName}" = x"Darwin"; then
-        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: found" >&5
+RSysinfoName=$("${R_HOME}/bin/Rscript" --vanilla -e 'cat(Sys.info()["sysname"])')
+if test x"${RSysinfoName}" = x"Darwin"; then
+    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: found" >&5
 printf "%s\n" "found" >&6; }
-        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for macOS Apple compiler" >&5
+    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for macOS Apple compiler" >&5
 printf %s "checking for macOS Apple compiler... " >&6; }
-
-        apple_compiler=$($CXX --version 2>&1 | grep -i -c -e 'apple llvm')
-
-        if test x"${apple_compiler}" = x"1"; then
-            { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: found" >&5
-printf "%s\n" "found" >&6; }
-            { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: OpenMP unavailable and turned off." >&5
-printf "%s\n" "$as_me: WARNING: OpenMP unavailable and turned off." >&2;}
-            can_use_openmp="no"
-        else
-            { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: not found" >&5
-printf "%s\n" "not found" >&6; }
-            { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for clang compiler" >&5
-printf %s "checking for clang compiler... " >&6; }
-            clang_compiler=$($CXX --version 2>&1 | grep -i -c -e 'clang ')
-
-            if test x"${clang_compiler}" = x"1"; then
-                { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: found" >&5
+    apple_compiler=$($CXX --version 2>&1 | grep -i -c -e 'apple llvm')
+    if test x"${apple_compiler}" = x"1"; then
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: found" >&5
 printf "%s\n" "found" >&6; }
-                { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for OpenMP compatible version of clang" >&5
-printf %s "checking for OpenMP compatible version of clang... " >&6; }
-                clang_version=$(${CXX} -v 2>&1 | awk '/^.*clang version/ {print $3}')
-
-                case ${clang_version} in
-                    4.*|5.*|6.*|7.*|8.*|9.*|10.*|11.*)
-                        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: found and suitable" >&5
-printf "%s\n" "found and suitable" >&6; }
-                        can_use_openmp="yes"
-                    ;;
-                    *)
-                        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: not found" >&5
-printf "%s\n" "not found" >&6; }
-                        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: OpenMP unavailable and turned off." >&5
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: OpenMP unavailable and turned off." >&5
 printf "%s\n" "$as_me: WARNING: OpenMP unavailable and turned off." >&2;}
-                        can_use_openmp="no"
-                    ;;
-                esac
-            else
-                { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: not found" >&5
-printf "%s\n" "not found" >&6; }
-                { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: unsupported macOS build detected; if anything breaks, you keep the pieces." >&5
-printf "%s\n" "$as_me: WARNING: unsupported macOS build detected; if anything breaks, you keep the pieces." >&2;}
-            fi
-        fi
-    else
-        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
-printf "%s\n" "no" >&6; }
+        can_use_openmp="no"
     fi
-
-fi # if test x"${openmp_already_works}" = x"no"
-
-## Check for suitable LAPACK_LIBS
-{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking LAPACK_LIBS" >&5
-printf %s "checking LAPACK_LIBS... " >&6; }
-
-## external LAPACK has the required function
-lapack=$(${R_HOME}/bin/R CMD config LAPACK_LIBS)
-hasRlapack=$(echo ${lapack} | grep lRlapack)
-
-## in what follows below we substitute both side of the define/undef
-## while this may seem a little unusual we do it to fully reproduce the
-## previous bash-based implementation
-
-if test x"${hasRlapack}" = x""; then
-    ## We are using a full Lapack and can use zgbsv -- so #undef remains
-    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: system LAPACK found" >&5
-printf "%s\n" "system LAPACK found" >&6; }
-    ## arma_lapack="#undef ARMA_CRIPPLED_LAPACK"
 else
-    ## We are using R's subset of Lapack and CANNOT use zgbsv etc, so we mark it
-    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: R-supplied partial LAPACK found" >&5
-printf "%s\n" "R-supplied partial LAPACK found" >&6; }
-    ## AC_MSG_WARN([Some complex-valued LAPACK functions may not be available])
-    ## arma_lapack="#define ARMA_CRIPPLED_LAPACK 1"
-fi
-
-## Default the OpenMP flag to the empty string.
-## If and only if OpenMP is found, expand to $(SHLIB_OPENMP_CXXFLAGS)
-openmp_flag=""
-
-## Set the fallback, by default it is nope
-arma_have_openmp="#define ARMA_DONT_USE_OPENMP 1"
-
-if test x"${openmp_already_works}" = x"yes"; then
-    arma_have_openmp="#define ARMA_USE_OPENMP 1"
-    openmp_flag='$(SHLIB_OPENMP_CXXFLAGS)'
+    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: not found" >&5
+printf "%s\n" "not found" >&6; }
 fi
 
 if test x"${can_use_openmp}" = x"yes"; then
@@ -3424,6 +3310,7 @@ printf %s "checking for OpenMP... " >&6; }
         { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: missing" >&5
 printf "%s\n" "missing" >&6; }
         arma_have_openmp="#define ARMA_DONT_USE_OPENMP 1"
+        openmp_flag=""
     else
         { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: found and suitable" >&5
 printf "%s\n" "found and suitable" >&6; }
@@ -3432,9 +3319,7 @@ printf "%s\n" "found and suitable" >&6; }
     fi
 fi
 
-
 ## now use all these
-## AC_SUBST([ARMA_LAPACK],["${arma_lapack}"])
 ARMA_HAVE_OPENMP="${arma_have_openmp}"
 
 OPENMP_FLAG="${openmp_flag}"
diff --git a/configure.ac b/configure.ac
index 9c315336..c2083efe 100644
--- a/configure.ac
+++ b/configure.ac
@@ -30,11 +30,11 @@ AC_PROG_CXX
 
 ## Is R already configured to compile things using OpenMP without
 ## any extra hand-holding?
-openmp_already_works="no"
+#openmp_already_works="no"
 
 ## default to not even thinking about OpenMP as Armadillo wants a pragma
 ## variant available if and only if C++11 is used with g++ 5.4 or newer
-can_use_openmp="no"
+#can_use_openmp="no"
 
 ## Ensure TMPDIR is set.
 AC_MSG_CHECKING([whether we have a suitable tempdir])
@@ -63,128 +63,33 @@ EOF
 if test x"$?" = x"0"; then
     AC_MSG_RESULT([yes])
     openmp_already_works="yes"
+    arma_have_openmp="#define ARMA_USE_OPENMP 1"
+    can_use_openmp="yes"
 else
     AC_MSG_RESULT([no])
+    openmp_already_works="no"
+    arma_have_openmp="#define ARMA_DONT_USE_OPENMP 1"
+    can_use_openmp="no"
 fi
 
 ## Go back home.
 cd "${owd}"
 rm -rf "${BUILDDIR}"
 
-## If the above checks failed, then perform other heuristics
-## based on the compiler version, etc.
-if test x"${openmp_already_works}" = x"no"; then
-
-    ## Check the C++ compiler using the CXX value set
-
-    ## If it is g++, we have GXX set so let's examine it
-    if test "${GXX}" = yes; then
-        AC_MSG_CHECKING([whether g++ version is sufficient])
-        gxx_version=$(${CXX} -v 2>&1 | awk '/^.*g.. version/ {print $3}')
-        case ${gxx_version} in
-            1.*|2.*|3.*|4.0.*|4.1.*|4.2.*|4.3.*|4.4.*|4.5.*|4.6.*|4.7.0|4.7.1)
-                 AC_MSG_RESULT([no])
-                 AC_MSG_WARN([Only g++ version 4.7.2 or greater can be used with RcppArmadillo.])
-                 AC_MSG_ERROR([Please use a different compiler.])
-            ;;
-            4.7.*|4.8.*|4.9.*|5.0*|5.1*|5.2*|5.3*)
-                 AC_MSG_RESULT([yes, but without OpenMP as version ${gxx_version} (Armadillo constraint)])
-                 ## we know this one is bad
-                 can_use_openmp="no"
-            ;;
-            5.4*|5.5*|5.6*|5.7*|5.8*|5.9*|6.*|7.*|8.*|9.*|1?.*)
-                 AC_MSG_RESULT([yes, with OpenMP as version ${gxx_version}])
-                 ## we know this one is good, yay
-                 can_use_openmp="yes"
-            ;;
-            *)
-                 AC_MSG_RESULT([almost])
-                 AC_MSG_WARN([Compiler self-identifies as being compliant with GNUC extensions but is not g++.])
-                 ## we know nothing, so no
-                 can_use_openmp="no"
-            ;;
-        esac
-    fi
-
-    ## Check for Apple LLVM
-
-    AC_MSG_CHECKING([for macOS])
-    RSysinfoName=$("${R_HOME}/bin/Rscript" --vanilla -e 'cat(Sys.info()[["sysname"]])')
-
-    if test x"${RSysinfoName}" = x"Darwin"; then
+## Additional Apple check
+AC_MSG_CHECKING([for macOS])
+RSysinfoName=$("${R_HOME}/bin/Rscript" --vanilla -e 'cat(Sys.info()[["sysname"]])')
+if test x"${RSysinfoName}" = x"Darwin"; then
+    AC_MSG_RESULT([found])
+    AC_MSG_CHECKING([for macOS Apple compiler])
+    apple_compiler=$($CXX --version 2>&1 | grep -i -c -e 'apple llvm')
+    if test x"${apple_compiler}" = x"1"; then
         AC_MSG_RESULT([found])
-        AC_MSG_CHECKING([for macOS Apple compiler])
-
-        apple_compiler=$($CXX --version 2>&1 | grep -i -c -e 'apple llvm')
-
-        if test x"${apple_compiler}" = x"1"; then
-            AC_MSG_RESULT([found])
-            AC_MSG_WARN([OpenMP unavailable and turned off.])
-            can_use_openmp="no"
-        else
-            AC_MSG_RESULT([not found])
-            AC_MSG_CHECKING([for clang compiler])
-            clang_compiler=$($CXX --version 2>&1 | grep -i -c -e 'clang ')
-
-            if test x"${clang_compiler}" = x"1"; then
-                AC_MSG_RESULT([found])
-                AC_MSG_CHECKING([for OpenMP compatible version of clang])
-                clang_version=$(${CXX} -v 2>&1 | awk '/^.*clang version/ {print $3}')
-
-                case ${clang_version} in
-                    4.*|5.*|6.*|7.*|8.*|9.*|10.*|11.*)
-                        AC_MSG_RESULT([found and suitable])
-                        can_use_openmp="yes"
-                    ;;
-                    *)
-                        AC_MSG_RESULT([not found])
-                        AC_MSG_WARN([OpenMP unavailable and turned off.])
-                        can_use_openmp="no"
-                    ;;
-                esac
-            else
-                AC_MSG_RESULT([not found])
-                AC_MSG_WARN([unsupported macOS build detected; if anything breaks, you keep the pieces.])
-            fi
-        fi
-    else
-        AC_MSG_RESULT([no])
+        AC_MSG_WARN([OpenMP unavailable and turned off.])
+        can_use_openmp="no"
     fi
-
-fi # if test x"${openmp_already_works}" = x"no"
-
-## Check for suitable LAPACK_LIBS
-AC_MSG_CHECKING([LAPACK_LIBS])
-
-## external LAPACK has the required function
-lapack=$(${R_HOME}/bin/R CMD config LAPACK_LIBS)
-hasRlapack=$(echo ${lapack} | grep lRlapack)
-
-## in what follows below we substitute both side of the define/undef
-## while this may seem a little unusual we do it to fully reproduce the
-## previous bash-based implementation
-
-if test x"${hasRlapack}" = x""; then
-    ## We are using a full Lapack and can use zgbsv -- so #undef remains
-    AC_MSG_RESULT([system LAPACK found])
-    ## arma_lapack="#undef ARMA_CRIPPLED_LAPACK"
 else
-    ## We are using R's subset of Lapack and CANNOT use zgbsv etc, so we mark it
-    AC_MSG_RESULT([R-supplied partial LAPACK found])
-    ## AC_MSG_WARN([Some complex-valued LAPACK functions may not be available])
-    ## arma_lapack="#define ARMA_CRIPPLED_LAPACK 1"
-fi
-
-## Default the OpenMP flag to the empty string.
-## If and only if OpenMP is found, expand to $(SHLIB_OPENMP_CXXFLAGS)
-openmp_flag=""
-
-## Set the fallback, by default it is nope
-arma_have_openmp="#define ARMA_DONT_USE_OPENMP 1"
-
-if test x"${openmp_already_works}" = x"yes"; then
-    arma_have_openmp="#define ARMA_USE_OPENMP 1"
-    openmp_flag='$(SHLIB_OPENMP_CXXFLAGS)'
+    AC_MSG_RESULT([not found])
 fi
 
 if test x"${can_use_openmp}" = x"yes"; then
@@ -195,6 +100,7 @@ if test x"${can_use_openmp}" = x"yes"; then
     if test x"${hasOpenMP}" = x""; then
         AC_MSG_RESULT([missing])
         arma_have_openmp="#define ARMA_DONT_USE_OPENMP 1"
+        openmp_flag=""
     else
         AC_MSG_RESULT([found and suitable])
         arma_have_openmp="#define ARMA_USE_OPENMP 1"
@@ -202,9 +108,7 @@ if test x"${can_use_openmp}" = x"yes"; then
     fi
 fi
 
-
 ## now use all these
-## AC_SUBST([ARMA_LAPACK],["${arma_lapack}"])
 AC_SUBST([ARMA_HAVE_OPENMP], ["${arma_have_openmp}"])
 AC_SUBST([OPENMP_FLAG], ["${openmp_flag}"])
 AC_CONFIG_FILES([inst/include/RcppArmadillo/config/RcppArmadilloConfigGenerated.h src/Makevars])
diff --git a/inst/NEWS.Rd b/inst/NEWS.Rd
index ccfed639..ed8b2a85 100644
--- a/inst/NEWS.Rd
+++ b/inst/NEWS.Rd
@@ -14,6 +14,7 @@
       \item Reworked detection of aliasing, leading to more efficient
       compiled code
     }
+    \item OpenMP detection in \code{configure} has been simplified
   }
 }
 
diff --git a/src/Makevars.in b/src/Makevars.in
index c50b481f..5922ebc0 100644
--- a/src/Makevars.in
+++ b/src/Makevars.in
@@ -1,5 +1,4 @@
 ## -*- mode: makefile; -*-
-
 PKG_CPPFLAGS = -I../inst/include -DARMA_USE_CURRENT
 PKG_CXXFLAGS = @OPENMP_FLAG@
 PKG_LIBS= @OPENMP_FLAG@ $(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS)
diff --git a/src/Makevars.win b/src/Makevars.win
index 6096d2ac..26f31d66 100644
--- a/src/Makevars.win
+++ b/src/Makevars.win
@@ -1,4 +1,3 @@
 ## -*- mode: makefile; -*-
-
 PKG_CXXFLAGS = -I../inst/include -I. $(SHLIB_OPENMP_CXXFLAGS) -DARMA_USE_CURRENT
 PKG_LIBS = $(SHLIB_OPENMP_CXXFLAGS) $(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS)