Totally depends on the instance. There are definitely furry communities here in Lemmy and they definitely feel lonely. But I have heard of some furry mastodon instances that actually are lively and active. No idea if they actually are since I don’t have a clue why I can’t access my mastodon account, let alone what instance I signed up on.
But active non-Linux, non-Star Trek meme groups definitely are a thing, despite how small they are.