Personally, I'm very disappointed Matrix devs still haven't solved decentralized user accounts. Users have no resiliency for their homeserver being unaccessible. It means now to prepare for outernet severance those who chose Matrix in Russia need to organize mass reregistering and reconfiguring of clients (most don't use local servers), which is practically unfeasible and means total disruption of local communication network for them.

On the other hand, most popular messengers will stop working altogether.

I'm also interested in an assessment of Tox and GNU Jami from this angle.