While on Reddit I love r/askhistorians and how well it was managed. Is there any niche community like them?

For historical questions concerning language, feel free to use !linguistics@mander.xyz. It's by no means a big or well-organised comm, but given that the mod there (me) has a hard-on for Historical Linguistics, you'd get at least some answer.

!askhistorians@lemmy.world is the largest, below is screenshot of search results

Ask Lemmy. The community will naturally branch a topic off of it gets too popular.

Yeah, that was one of my favorites. Haven't seen anything similar

You mean on Lemmy? Lemmy itself is a niche community. I believe there are some far left political niches on lemmy.ml and lemmygrad.ml but I haven't checked into them. They discuss the fine points of whatever.