Hubzilla: ActivityPub
ActivityPub in Hubzilla (PubCrawl)
Hubzilla integrates with ActivityPub using the PubCrawl addon. This can be turned on or off by the admin and the user.
Conversation Containers
Hubzilla 10 will implement Mike Macgirvin's Conversation Containers.
Handling of Clones over ActivityPub
Hubzilla and Nomad Protocol have something that ActivityPub currently does not: Nomadic Identity.
The basic concept is that in Hubzilla, your channel can reside on more than one server and have more than one channel address. Hubzilla calls them clones since they are synced. One of those channels is designated as the primary channel. People can follow any of your clones and receive the same messages.
Since some platforms do not recognize nomadic identity, Hubzilla has to send ActivityPub messages in a specific way.
First, it does list the clones as aliases when people query WebFinger. And platforms that want to check to see if there are aliases can do so.
Second, over ActivityPub, people follow one or more of your clones. Since this may not be your primary clone, Hubzilla will sync the clones and then have the appropriate clone send out the message.
For example, if your primary clone is on primary@example.com and your clone is clone@example.social, when you post, the primary clone will send messages to followers to primary@example.com and your clone will send messages from clone@example.social to followers of clone@example.social.
From their perspective, they are still following the same account.
You will have to maintain your clones in order to maintain your old ActivityPub followers. Otherwise they will be following you on a server that you no longer post from.
If they follow two clones, they will get two copies of all of your posts, one from each domain and from a different sender.
This may explain why there is sometimes a delay when people get messages from you. If you post something on your primary account but they are following you on your clone, the clones must first sync before the messages are sent over ActivityPub.
Comparision to how Nomad Protocol handles it
It should be noted that people following you over Nomad protocol don't have the same issue because it understands the concept of nomadic identity and clones. The server where you posted the message will send the message to all of your Nomad protocol followers, and since your keys and hash matches, they know it was from you even when coming from a different domain.