CKEditor5 will replace CKEditor4 in core when Drupal 10 is released. A stable version will be released and included as of Drupal 9.3 getting the experimental designation. However, CKEditor 5 can already be installed as a contrib module and used with versions of Drupal 9 which are 9.2 and greater. I've been running CKEDitor 5 on 9.2.0-alpha1 and 9.3.x-dev. Features were demonstrated back on March 11, 2021 and the ckeditor5_layercake module from Tim Plunkett is one of the modules available.
is it possible to use Group for this scenario: the global content admin user creates article, associate article to group. The member of group can only view article is belongs to the group? very appreciated!