Pinball is a personal hobby of mine, and there's no shortage of active forums -- Pinside, Tilt Forums, even rec.games.pinball still sees daily posts. /r/pinball exists, of course, but you'd be hard pressed to find many folks who treat it as a daily destination.
You'll find a lot of similar spaces in other hobbies.
Back in the day, if I typed in "Radiohead" or "guitar pedal schematics" I would find forums or personal sites about these topics.
Now I will find (1.) Stores (2.) Content aggregators
Those niche forums and websites likely still exist, but it isn't obvious how to find them.
The ones I frequent are insulated from the wider internet. The fact that these places are absorbed into the structure of Reddit is a shame: while it's easier, the discussion is constrained by what is possible on the platform. Static content is difficult to maintain, like discussions of album errata or the history of some circuit.
This is probably just bias for the late-90s.
Hey DDG peeps, if you stumble upon this comment: make a forums-only filter!
But seriously, thanks for saving me from my own idiocy.
I really miss Google's "Discussion" search filter.
I'm starting to feel like that is what allows them to survive as communities. It's a weird balance: too little visibility and your forum dies from attrition; too much and the conversation devolves into, well, Reddit. (This is true even within Reddit: the smaller and more obscure the sub the less likely it is to be a garbagefire.)
I'm not optimistic about general-purpose search engines, TBH. As the userbase of a search engine increases, so does the incentive to game it with SEO garbage - and preventing SEO garbage feels isomorphic security, except you can't even hold out hope for formal verification.
Linguistics has people who compile lists of resources, and there's enough of a community that if I'm trying to find something, I can ask around and someone might know. Google is sometimes useful, but it's a hell of a slog to get anything out of it, and that's with years of experience in what long lists of keywords to type in to cut through some of the crap.