Try this

.github/workflows/tests.yml

@@ -156,20 +156,27 @@ jobs:
           ini-values: sendmail_path=/usr/sbin/sendmail -t -i, error_reporting=E_ALL, display_errors=On
           extensions: ${{ steps.set_extensions.outputs.EXT }}
 
+      # Move the test dependencies to non-dev to prevent the install getting blocked by missing extensions
+      # for dependencies which are not needed for the test run.
+      - name: 'Composer: temporarily move the test dependencies'
+        if: ${{ matrix.extensions != 'optimal' }}
+        run: composer require yoast/phpunit-polyfills:"^1" --no-interaction --no-update
+
       # Install dependencies and handle caching in one go.
       # @link https://github.com/marketplace/actions/install-php-dependencies-with-composer
       - name: Install PHP packages - normal
         if: ${{ matrix.php != '8.4' }}
         uses: "ramsey/composer-install@v3"
         with:
+          composer-options: --no-dev
           # Bust the cache at least once a month - output format: YYYY-MM.
           custom-cache-suffix: $(date -u "+%Y-%m")
 
       - name: Install PHP packages - ignore-platform-reqs
         if: ${{ matrix.php == '8.4' }}
         uses: "ramsey/composer-install@v3"
         with:
-          composer-options: --ignore-platform-reqs
+          composer-options: --no-dev --ignore-platform-reqs
           # Bust the cache at least once a month - output format: YYYY-MM.
           custom-cache-suffix: $(date -u "+%Y-%m")