One option is them being tied together while remaining separate. Like have the clients all treat them as one channel on the client side, with them still all being separate on the server end.
I think the main problem people want dealt with is when they are in 7 of the same community accross different servers and someone cross posts something to all 7 of them. I don’t know if we’ll ever be able to solve that problem on the user end, like discouraging cross posts or whatever, but there could be a way that posting to one automatically and invisibly crossposts to all the channels that are deemed “like” that one. Whether communities could have tags that align with post tags, or something like that. I don’t know. But it sucks that right now the option is either pick one and deal with missing out on anything not cross posted, or pick a few and deal with all the things you see multiple times.