Ttrpg.network seems to work well. As does the Star Trek one, even despite serious problems with some of their communities’ moderators that the admins have failed to take action on.
I think it’s a format that can make sense especially if there’s a broad range of specific communities around a central topic. Like ttrpg.network can have communities dedicated to each RPG, one for memes, for art, for broader conversation about the hobby, etc. It means you know if you want something RPG-related, that’s the instance to look for.
In a way, you could even say all the various country instances, including my own home insurance, are doing the same thing. What is a country instance if not “entire instance devoted to one area”?
I actually deliberately avoided mentioning the Troubles because I wanted to bring up cases where everyone today could fairly uniformly agree that we were discussing freedom fighters more than terrorists. Too many today would still say that the Provisional IRA were the bad guys (or at the very least that they were “as bad as” the other side). But the point I wanted to make was how given enough time, even terroristic actions can end up being viewed on the whole as coming from the “good guys”, if their cause is viewed as just.
I could also have mentioned American revolutionaries.