Several of he hobby ones. Ben Eater (6502 based computers, 8 bit computer), local ones, history/science based ones, infosec/sysadmin/etc. ones. There are some Lemmy based ones, but it'll take a while to build up. I'm hoping that I can contribute to them and see them grow a bit. But, others are just where I could comment and enjoy as I lack the real knowledge to contribute very much (the history/science ones that required more in-depth knowledge and not just a "Wikipedia degree of arts of internet research for obscure questions".