This module is different from Message Digest in a couple of ways:
- It's a standalone module meant to provided an all-in-one solution for generating notifications, where Message Digest is part of an ecosystem of modules that comprise the Message stack, and not all of them have been ported to Drupal 9
- Digest is really designed to send notifications about new content, though it seems built around views, so anything that can be listed in a view can be included in a digest