Roman Z
--- a/config_override_warn.module
+++ b/config_override_warn.module
      '#theme' => 'config_override_warn_overrides',
      '#overrides' => $overrides,
    ];
-    $warning = \Drupal::service('renderer')->renderPlain($override_output);
+    /** @var \Drupal\Core\Render\RendererInterface $renderer_service */
+    $renderer_service = \Drupal::service('renderer');
+    $warning = version_compare(\Drupal::VERSION, '10.3', '<') ? $renderer_service->renderPlain($override_output) : $renderer_service->renderInIsolation($override_output);