> essentially XMPP with Conversations is all we have in this arena right now.
Maybe this isn't too bad. How does modern XMPP compare with Signal's protocol?
Since Signal refuses to learn from XMPP (especially the federated part), maybe the solution is to make XMPP learn from Signal. Then, Signal's failure to become federated would have been an important step to make XMPP finally useful for secure messaging.