I spent days worth of reseach some years ago trying to find a reddit alternative (think pre-pandemic, well before consensus started to turn). I more or less found a few substitutes (which includes HN), but nothing that ever truly felt like "community".

As you implied here, the sad fact is that a lot of the niche groups live within the mainstream. on a Discord server, or a subreddit, or Facebook group. And I've moved away from most of those. Probably need to move away from Discord in time too.

Either way, still never made a friend that way.