Not equivalent exactly, but the fediverse or IRC have been fun places for me to chat about some hobbies. gemini is another option. I think people write gemlogs on there and then others write some in response. I only use gemini a little bit, and just as a reader.

Something like IRC for chatting combined with a wiki to manage info related to the hobby could work well.

You could also treat Reddit like reading a book or Wikipedia and choose not to contribute. Go there to learn something, bring the info back to your own space you're building that has people you'd rather be around.