Only one, clubhouse. I talked to some very great minds, Abe Caplan was talking to us about his research in BMIs on braingate for instance, Paul King used to host weekly neuroscience rooms, and lots of people working on interesting projects. Most of it isn’t, but it’s all audio, doesn’t really have scaling problems or the ability to as much as sites and wisdom I’ve heard is good too, I’m a fan of audio social media.
Site based HN is one, github if you program, best not using it at all. Social media is a structure and it’s always the same effect, you’re only using it because everyone else is on it she since nobody is on urbit, mastodon, matrix etc there’s no “social”. Find your interests and adapt to it, I only joined Keybase discord and telegram to talk to some people who use it.