There’s less. Especially forum type stuff. I can list a few interesting sites though.

https://cs.rin.ru/ - Site for peg legged discussions about games basically.

https://www.shiey.com/videos - guy who does like urbex and stuff who made his own site because youtube kept taking his videos down. Also has a blog on there.

Substacks too. This is more of a category. A lot of independent reporters have their own substack pages where they’ll post articles.

Matrix is another one. It’s like a fediverse chat alternative. Similar to discord but structured like lemmy.

https://archiveofourown.org/ - website for community made written works. Fan fictions, or original stuff. Has a pretty good search function so you can find anything that interests you, and has some discussion methods like comments on works. Altho most of that will probably be done on secondary sites.

Another category is Linux forums. Probably one of the largest still existing types of forums. Places where people go to discuss issues with their Linux distros, and share fixes. Aswell as software development in general for Linux.

One thing i like to do too is explore the Chinese internet. Places like BilliBilli, QQ, Weibo. It’s similar, but also different to the big sites in the west, and can be fun to explore.

Also while its not done as much, and traffic to them is lower now hosting your own small site is easier than it’s ever been. So if theres a site you’d like to see you could always make it yourself. You can rent cloud hosting, or use an old pc or something. Then all you need is a few like minded people to get on there with you.