go to your search engine and type "[interest/hobby] forum" and you'll find a selection of sufficiently active vbulletin forums, communities, and groups. Random examples -
There's all kinds car forums that are still around from the 90's that have maintained a community for 20+ years and are the authoritative source of repair info for many classic models. It makes you weep for the endless amount of expertise and congregated knowledge that is now being locked away in these social media walled gardens and private chat apps like Discord.
There are some hobby and sport-specific ones out there, Slowtwitch for Triathletes and Teton Gravity Research for skiers/mountain bikers. Both still pretty active!
This is an odd question. There are tons of active discussion boards that can be found with trivial effort. Other replies have mentioned forums for specific auto makes and models, and you'll find they get spun up quite quickly when a new model comes out, and attract a lot of traffic. I don't think anyone has mentioned Steam discussion boards yet. Heck, Facebook is a discussion board in many respects.
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[ 6.1 ms ] story [ 160 ms ] threadedit: and now that I've switched teams, I'll plug NPORA (nissan pathfinder off road association).
I actually know lawyers who read flashback for a sort of crowd sourced case info. You just have to wade through the casual racism.
https://www.rvforum.net/
https://www.woodworkingtalk.com/
https://www.benzworld.org/forums/
etc...
They're not general interest entertainment forums, but there's a lot of specialist knowledge about analog to digital video conversion.
Habr
https://www.tacomaworld.com/
But to the point of the OP, HFBoards.com is a hockey forum and is still very active.