Matrix works, and has fairly easy-to-use clients (and I've switched a few non-technical folks without too much trouble). It's also an open protocol, not just an app.
The main criticism (and I'm preemptively responding to tptacek here) is that they haven't yet made E2EE the default (though this should happen in a few weeks now that cross-signing appears to be done). I also think the key backup system should be much better explained -- there is a usability bug open for it and I've posted some suggestions.
The main criticism (and I'm preemptively responding to tptacek here) is that they haven't yet made E2EE the default (though this should happen in a few weeks now that cross-signing appears to be done). I also think the key backup system should be much better explained -- there is a usability bug open for it and I've posted some suggestions.