tbf they’re pretty much all federated with each other still, there’s not a whole ton of exceptions. You’ve got the fascist and tankie kids, they’re defederated a good bit, and Beehaw defederated the two other big ones, due to bot accts if I remember right.
Basically anything asides world, ml (i think?), beehaw, lemmygrad or explodingheads.
You can google lemmymap, and you’ll get a visual representation that shows blocks. There’s also a couple websites that’ll give the info more accessibly, but I don’t recall them. Someone else will prob share one.