PieFed.

I'll mention some dead projects, in case anyone gets an itch to pick them up...

lotide/hitide is a minimalist, text-only platform. It has been abandoned.
https://sr.ht/~vpzom/lotide/. https://lotide.fbxl.net/

Sublinks was in the works, but it is on indefinite hiatus. As I understand it, the main dev became too busy IRL to continue work.
https://github.com/sublinks

Piefed, Mbin.

PieFed, Kbin died but lives on in its fork Mbin, Sublinks didn't pan out but was started (the PHP code is FOSS), nodeBB, and flarum.

You may also occasionally see posts from Friendica or Mastodon that also use the ActivityPub protocol, though the barriers to sharing those with the Threadiverse are somewhat high.

Mbin, Piefed and NodeBB

Mbin can also be used for microblogging.

There's NodeBB if you want a forum/BBS style UX for the threadiverse!

Brutalinks does not have separate communities, so it works more like HackerNews/lobste.rs

Know this isn't a suggestion post but it made me think of what I wish was being worked on. Might as well try to tackle webdev and fail as I'm unemployed lol.

Kinda wish we had a torn like lemmy (im very late to discovering that game lol), some of its features are appealing, think itd be fun to gamify social media, like temp bans put users in jail and you could see all the users in jail currently (get real extra with it and let ppl vouch for ppl tying their account status to theirs for the remaining duration of the ban in case of new infractions and bail them out)

Piefed already does trust value, having different tags at different values that could be customized per instance could be fun. Like 10% troll - 100% saint on one.

Be a fun way to use a point type system on purely meaningless stuff, I do like that there is no realworld value at all in that game (bannable), just a fun little dopamine hit of numbers and images. Encourage donations through that.

Tildes.