I have been on twtxt for a long time, https://twtxt.app/. Very niche, very small, I love it!

@fastidious20 notes102 replies5 tags, 3 users following4 followersBetter don’t ask, just fastidious.enter to follow5d · 2 repliesenter to reply

Organically. Also not growing isn’t a bad thing. Was the aim to be huge? I have witnessed that smaller communities last longer, and work better. Knowing the people you interact with is a perk.