A couple things about the content of this post, that people aren't talking about. Mastering Emacs by Mickey Petersen is a solid book on Emacs and a good companion to the official manual. Mickey usually has an update to Mastering Emacs not long after a new version is released, which is great. I'm thankful for his many contributions to the Emacs community, and I really enjoyed reading his thoughts on the new features and additions to Emacs 28.
Secondly, the breadth of the changes in Emacs 28.1 is staggering, especially considering that Emacs 27.1 was released some 19 months ago. I think it's safe to say that despite all the hand-wringing about the antiquated email-centric way that Emacs is developed, an impressive amount of work is getting done. Emacs development is alive and well.