Got to love the Fediverse. All my inner circle are on different, mostly obscure, self-hosted and even self-rolled ins...

Got to love the Fediverse. All my inner circle are on different, mostly obscure, self-hosted and even self-rolled instances. They all use the same standard web protocols and activitypub infrastructure – or do they? In theory we should all be able to see and hear each other. But can we?