I don't see it as needing a solution. I can subscribe to five hiking/camping communities across various instances, posts show up in my "subscribed" feed, and I don't really care I'm looking at multiple communities. I care about the topic, not the instance.

I picked an instance that has reasonable rules that I believe will play well federating with other civil instances. Its a feature, not a bug, that I've found multiple communities focused on my hobby.