

The two that I have had the most success were both hobbies I enjoyed that had a regular group that happens weekly. One was an in person weekly DnD game at a local game shop. It was great to chat about TTRPGs DnD and other nerdy things with everyone since I loved it. (It was in Chicago and few of the older people played with Gygax which was awesome.)
The second was a weekly distance running group that I am still kind of a part of. We run for an hour for a similar route and then go out for pizza. It was great to chat with whoever was my own speed. when running and then with everyone for food afterwards. I do some endurance sports and it was fun to hear about all the crazy things the really good ones did.
Both were weekly, in person and were things I was interested about. These are the key
I think with that is an unexpected inflection point that looks inevitable in hindsight where one network dies and another thrives. It happened with Digg and Myspace. You if you focus on long term organic growth it can happen but unknown when