I got some forums to contribute!
Terraria Community Forums | Official forum for the game Terraria and tModLoader.
TFW2005’s Boards | Forum that is all about the Transformers franchise, and has been around AND still active since 2003.
Dragon Cave Forums | Official forums for Dragon Cave, where users can trade Dragons and whatnot.
Frutiger Aero Archive Forums | Forum for discussing Frutiger Aero and related aesthetics.
I’m also not sure how to edit the original post, but here are some additions:
It’s cool that a frutiger aero forum exists. Maybe I’ll join…
i co-own a forum! can’t seem to add it, probably because i’ve just created this acct lol
YellowTealPurple.net - a general art and discussion forum for creatives
one thing i sometimes dream about is to create some kind of webring or network specifically for forums.. if there are any other forum webmasters or admins who’d be interested in that, i’d love to hear from you!
i found this forum through their bluesky page following me. the forum is called vampfreaks and its basically a forum for goth/alternative people.
Is this a new version of the old Vampire Freaks site?
i guess maybe but i didn’t hang out on the original vampire freaks so i wouldn’t know
Cookdandbombd - Dedicated to British comedy shows but has all the usual boards too, with a community of regulars.
Oh I can add it myself! Neat.
I just added two forums focussed on books (one ebooks, the other mainly physical books). Not sure what the flags are about because UK and US are far from the only countries most of the forums invite users from, and they’re also far from the only countries that speak English. So I didn’t add any flags.
I’ve got to ask, does anyone know of any craft forums with a good community? Craftster has been revived as Lettuce Crafts but it doesn’t look very active 
I don’t have anything useful to add here, other than that I find it so frustrating how few forums exist, across the board, but especially in spaces beyond gaming/technology. I’ve been searching for them lately, and I did find SDF, which is continuously-run Usenet. As I wrote this, I did remember that there is Foro Coches. Initially, it was a Spanish webforum based around cars, but I guess today it’s the largest webforum still hosted in Spain, with a larger range of topics.
Ravelry is still around if you’re a knitter or crocheter. Reddit in general is .. ugh … but their r/crossstitch community is pretty awesome!
DubCNN.com, the “Westcoast News Network”, was created in 2001 and still has an active forum to discuss music, mostly West Coast based hip hop.
The archives are fun to search through and read insights from various artists across the decades about particular times, albums etc.
I also have some forums to contribute!
https://gaminglatest.com/ - PS5, Xbox Series, PC & Nintendo Gaming Forum
https://administrata.net/ - an online community for; forum owners and community builders trade what actually works: management, growth, monetization, security, and the tech underneath it all.
https://forumpromotion.net/ - Forum Promotion is similar to Administrata as well. Along with https://www.theadminzone.com/
https://discussionhq.com/ - A general chat forum
https://www.roflmao.com/ - is similar to DiscussionHQ, they are both general discussion boards.
https://thee.zone/ is also similar to the above two.
https://astrowhat.com/ a Niche online community that is dedicated to the discussion of astronomy and astrophotography.
Film Lovers - an online community for film and television discussions.
https://prismatica.animerpgs.com/ - Anime & Roleplaying community.
https://jcodesresources.com/ - Official resource forum for Jcink(the forum software).
https://thehikingforum.com/ - forum for the discussion of, hiking, backpacking, other outdoor activities.
https://idlehands.discourse.group/ - Idle Hands is a forum for makers, gamers, amongst other things.
https://www.virtualpetlist.com - an online community dedicated to the discussion of virtual pet games & sim games.