From other such places. phpBB forums, imageboards, private trackers, webrings are good gateways.

How do you find those? I haven't been able to find an invite to a private tracker since my IRC days 20 years ago. PhpBB forums, are there any still around?

Idk. I believe you and I think you're right, but I don't even really know where to start even so

have interests. pull on threads. follow weird leads.

in some cases, build your own.