I use matrix. Every chat room I use is unencrypted and all have at least one matrix.org user. I assume it can be encrypted but the usability is such that in practice it's cleartext.
As a counterexample: I use Matrix along with ~30-50 people, on a federated server, and every room is encrypted. After sufficiently stressing to people that they need to save their secure backup key, we've had few problems with encryption usability.
(3) With sufficient thrust, pigs fly just fine. However, this is
not necessarily a good idea. It is hard to be sure where they
are going to land, and it could be dangerous sitting under them
as they fly overhead.