I'm "on" Mastodon
over here, though I don't actually post.
I'm ambivalent about Mastodon — even though it's not controlled by Elon Musk, I'm not sure it's a great idea to pour a bunch of stuff into that format to whoever controls the various instances. It's sort of a parallel to how I now think "MIT License by default" is a bad idea.
I don't think it's harming the world to read it, though, since you're not boosting an entity's advertising power and thereby its incentive to promote harmful stuff. I think it is bad for your brain to read in that format and to pay attention to boosts and likes, though. Some people only post there, though, so I have dipped my toe in.