They still to be attached to an instance at the protocol level. Or you have instances which are barely network components rather than communities, but that’s not what ActivityPub is about
However, there’s nothing stopping a developer from extending the protocol to support it. You can essentially throw a message into the fediverse with more or less arbitrary payloads. Adding something like a feed/community identifier is not impossible.
They still to be attached to an instance at the protocol level. Or you have instances which are barely network components rather than communities, but that’s not what ActivityPub is about
And that’s a problem.
However, there’s nothing stopping a developer from extending the protocol to support it. You can essentially throw a message into the fediverse with more or less arbitrary payloads. Adding something like a feed/community identifier is not impossible.