In practice, federation works _great_ when the apps all have the same basic structure, and gets pretty rough otherwise.
Mastodon instances basically _work great_ with each other, and with Friendica and Calckey too, since they have the same Twitter-like structure. Lemmy and Kbin - and all instances thereof - can chat with each other without issue too, since they have the communities + threads structure in common.
But trying to get Mastodon and Lemmy to talk to each other is 1. surprisingly possible, and 2. kind of annoying, since they speak the same protocol but have different structures of communication. And never mind other ActivityPub applications like BookWyrm or WriteFreely or PeerTube.
Mastodon instances basically _work great_ with each other, and with Friendica and Calckey too, since they have the same Twitter-like structure. Lemmy and Kbin - and all instances thereof - can chat with each other without issue too, since they have the communities + threads structure in common.
But trying to get Mastodon and Lemmy to talk to each other is 1. surprisingly possible, and 2. kind of annoying, since they speak the same protocol but have different structures of communication. And never mind other ActivityPub applications like BookWyrm or WriteFreely or PeerTube.