Every few days I’ll receive an e-mail asking if I know of any good communities in a specific topic.
I rarely do, not unless it’s a hobby of mine.
However, I can offer this pointer. Searching for “{topic} online community” probably wont get you good results. Try “{topic} chat” or “{topic} forum” or “{topic} fans” and other terms along those lines.
For example, searching for an online golf community is futile. Few communities call themselves communities (why is that?). Searching for Golf talk, golf chat, golf fans, golf forums. Will soon bring you a list of thriving online golf communities.
Good luck.