According to en.wikipedia.org/wiki/Fediverse:

The majority of Fediverse platforms are based on free and open-source software, and create connections between servers using the ActivityPub protocol. Some software still supports older federation protocols as well, such as OStatus, the Diaspora protocol and Zot. Diaspora* is the only actively developed software project classified under the original definition of Fediverse that does not support ActivityPub.[5][6]

You would have to look at those citations to see how authoritative they are.