I think beehaw is a special case where the number of communities is restricted and only admins can create them.

For ones outside of beehaw proper, you can check out askKbin as some folks regularly ask about communities and magazines there.

Edit: I meant @FindAKbin or https://kbin.social/m/FindAKbin

I think you can find a lot of what you are missing here: https://sub.rehab/?searchTerm=&visibleServices=lemmy&visibleServices=kbin&visibleServices=misc&visibleServices=matrix&officialOnly=false&newOnly=false