I went searching for this and the only thing I could find were more people looking for a community similar to r/twoxchromosomes so I created it. I’m not a mod or a creator of the original subreddit, if any of those people find this and would like to join as a mod, absolutely let me know.
I think it all depends on your instance. If I go on the website, not app of my instance, I can go up to the menu at the top and below “create post” there’s an option for “create a community.” I know some instances don’t allow users to create their own, you have to contact your instance admin to create it for you and appoint you as a mod.