My priority is this: if we start now developing public infra on ActivityPub in a federal system like Germany we end up like, ok every state runs its own activitypub instance. Then one state will drop out in the future, because they get a government that says I don't like whatever the previous government has done and will end this service and stop it.
The users will end up lost. Because they loose their public identity because it is domain based. All the references to content they produced might get lost.
That's why I think *any* domain based system is not suited for public infrastructure
