diff --git a/setup/plugins/init/StandaloneRiverlea.civi-setup.php b/setup/plugins/init/StandaloneRiverlea.civi-setup.php
new file mode 100644
index 000000000000..f8f95367c664
--- /dev/null
+++ b/setup/plugins/init/StandaloneRiverlea.civi-setup.php
@@ -0,0 +1,26 @@
+<?php
+/**
+ * @file
+ *
+ * Enable Riverlea by default on Standalone installs.
+ * - this does not *select* a Riverlea theme but removes one step for doing so
+ * - we set dark_mode setting to inherit instead of always light (which is the default for other CMS)
+ *
+ */
+
+if (!defined('CIVI_SETUP')) {
+  exit("Installation plugins must only be loaded by the installer.\n");
+}
+
+\Civi\Setup::dispatcher()
+  ->addListener('civi.setup.init', function (\Civi\Setup\Event\InitEvent $e) {
+    $model = $e->getModel();
+    if ($model->cms !== 'Standalone') {
+      return;
+    }
+    \Civi\Setup::log()->info(sprintf('[%s] Handle %s', basename(__FILE__), 'init'));
+
+    $e->getModel()->extensions[] = 'riverlea';
+    $e->getModel()->settings['riverlea_dark_mode_frontend'] = 'inherit';
+    $e->getModel()->settings['riverlea_dark_mode_backend'] = 'inherit';
+  });