Since apparently nobody reads what I write, I'll reiterate some points about the protocol stuff, as I see wrong information being spread around.
ActivityPub is a new W3C standard for federated messaging with better privacy support and more future-proofness.
v1.6 of Mastodon implements ActivityPub for the first time, and "prefers" this protocol when it's available. However there is no change at all to how OStatus works in it.
v2.0 will pull the switch on private toot federation over OStatus.