The same can be said about Reddit. I’m not subscribed to any of the big subreddits there. I use it for niche communities. To me, that’s the whole point!

Lemmy’s having some growing pains right now (spinning wheel of death) but I’m confident they’ll be resolved. At that point, it’ll be much nicer to use, so I’m pretty happy with that.

As for people hoping to one day “jump over,” I think that’s a mistake with almost anything. Dip your toe in, don’t go “all in” on anything you’ve never used before. You’re much less likely to end up extremely disappointed that way.

In my experience, private instances of PhpBB forums provide niche webtools that are necessary for community building that Reddit could never replace.

The Tetris community created a Javascript gui called Fumen (https://harddrop.com/fumen/), that can be embedded into PhpBB forums.

The chess community created Javascript GUIs that read/write .pgn files (aka: move-history files) to help the community discuss games.

The Go community created a similar GUI for Go games. Etc. etc.

-----------

Since the administrator controls the whole webpage (including Javascript), you can host local tools in a Reddit-like environment. I think people are sleeping on the potential here, especially if you've never used these custom web-GUIs before.