One thing I'm pretty much noticing when it comes to self-hosting in various communities.

Punks and similar indie musicians: Bandcamp (m'okay) and Facebook, nearly none have things like blogs or newsletters to get info about events. :/ Imagine advocating against capitalism/corporatism/… with being reliant on Facebook for organising yourselves.

Demoscene: Some blogs, ressource websites like pouet.net / demozoo, webradios, … sadly a lot of Twitch and Discord. ♥ CCC for hosting the streams of some of them.

FLOSS: Massive amount of Github and growing amount of Discord. Some self-hosted people, some on community sites, …
(btw even some GNU stuff is stuck to GitHub for sending patches)

Weeb communities: Oh no :( Used to be IRC and forums back in the day though.