I haven't seen an announcement, but a friend who uses the "Ubuntu Social" https://ubuntu.social/ #Mastodon instance reports that the instance will be shutting down soon.

He was concerned about the strict rules that most major Mastodon sites have, so I pointed out that he isn't limited to Mastodon. I also told him that there are some wide-open instances, but that they tend to attract some vile people. It is probably best to find an instance with rules that are "loose enough" to let you be yourself but strict enough to kick those vile people out.

I'm not a fan of dictatorial admins, but if you don't have some sort of rules, you get nicecrew.digital or poa.st (or left-wing equivalents of these right-wing sites).

One could easily wish that these extremists (right and left) would be exiled to some island, where they can torment one another but cannot contact the rest of us.