https://www.pbnation.com/forum.php – This shit still has posts I made on it back when I was fucking 14!

Internet car forums are the only reason my cars are still running. A trove of endless car information to fix things yourself and not let them become obsolete, where to find parts, what new parts fit old chassis, etc. Will forever be grateful for them

https://www.overclockers.com/forum is still going strong a small but dedicated group and a massive store of computer technology history.

May I recommend knockout.chat, a general forum, made by ex Facepunch members.

I’ve been very heavily involved with https://forums.ageofempires.com/ since Reddit kicked the bucket. I don’t love the fact that it’s controlled by a company with a very obvious bias, but apart from an overzealous language filter they seem to be pretty good at allowing very strong criticism…better than I’ve seen some companies that run their own subreddits be, anyway.

https://www.urban75.net/forums/ has been going for about 30 years.