Great question, I am wondering what other mediums anyone else is using, e.g., irc, slack, niche-topic discord, or weekly zooms. I have had taste of all of these, but I am yet to find something I can think completely satisfies. I know some local area hacker groups have slacks (but anyone can join them), and open-source projects or particularly niche projects have active discord servers/their own forums. Tbf, I mainly browse or lurk most places, or use HN for shitposting so I am not that well-versed.
Edit to add: you may also find that some mastodon servers are particularly suited for some topic you're interested in.