Reddit has subreddits. What does Lemmy go with?
My personal vote is for lemmings!
Edit: I am personally leaning towards Sublemmy now. It retains the context of being a forum under the general sphere of Lemmy and the connection to Reddit lets people know immediately what Lemmy is about. Thanks to @[email protected] for the comment!
Lemmy says what they call them in the title bar, so they already have a name, communities. Seems projects tend to use their own nomenclature, Kbin calls them magazines.
There’s no official term for Lemmy users. Lemmings would be appropriate, though not particularly flattering.