A lot of the anime-related communities have consolidated over time to the ani.social instance. There are historical reasons for this (largely due to hostility from the ml admins), and if you want a brief history for just the general anime community, I previously wrote a post here.
That being said, the ani.social instance has been growing with new communities being added. Here are the more active ones:
General Communities
Series-Specific Communities
- !dungeonmeshi@ani.social - Delicious in Dungeon community
- !frieren@ani.social - Frieren: Beyond Journey's End community
- !nokotan@ani.social - My Deer Friend Nokotan community (currently airing show)
- !dandadan@ani.social - Dan Da Dan community (show airs this fall)
- !dragonball@ani.social - Dragonball community
Misc.
- !vocaloid@ani.social - Very new community just started by @hisao@ani.social about vocaloids. Check it out!
- !vtubervids@ani.social - Community to discuss and share videos from and about vtubers
- !seiyuu@ani.social - Community about Japanese voice actors behind the scenes
This isn't surprising considering how popular the first season was, especially in Japan. The impression I got is that the production side was caught off-guard with its success, which could explain why it has taken a while to organize a season 2 if they weren't planning on it from the beginning.