Drupal::service('renderer')->renderPlain is deprecated since 10.3.0

The 8.x-1.x branch supports currently Drupal core from 9.2 to 10.3. The function renderInIsolation() was added only in Drupal core 10.3, therefore without BC break, we cannot merge this to 8.x-1.x. This deprecation was fixed in the new 2.0.0-beta1 release created today, which supports Drupal 11: https://www.drupal.org/project/xmlsitemap/releases/2.0.0-beta1 →