This isn’t niche at all, but gbatemp is fantastic. Lots of emulation, modding, romhacking, general gaming discission, etc.

3dprinting for sure. Friendly, informed and fast replies. Like it there.

I love all the gaming and nerd communities. Cause forums on my favorite games is my favorite part about Lemmy. /c/legendofzelda /c/starwars /c/stormlight /c/playstation

Sailing Anarchy for all things related to sailing. There’s a small subset of folks on there that are very toxic, but it is the best place for extremely technical content.