Community is a chicken-and-egg problem. I started my own Lemmy server to try to contribute and hold some space for discussion, but if you just want to start a community, it's as easy as making a new account on https://lemmy.world and clicking Create a Community on the front page.

For localllama this is the most active one so far (which isn't to say it is very active at all):

https://sh.itjust.works/c/localllama

If you post topics you'll generally get at least a few responses a day though.