It'd definitely be neat if there was a way to group those similar communities into single, shared communities between federated instances. Like, if 6 different instances have "Gaming" communities, to have them all effectively grouped into a single one, and also include the "Gaming" communities from any other instances that you federate with in the future.

I think the ideal UX would be to be able to see one "Gaming" community, subscribe to it, and check a box for "Include Similar Federated Communities" or something, and have posts from all of them show up in your feed, without having to individually subscribe to them.