Drew DeVault: I don't trust Signal https://drewdevault.com/2018/08/08/Signal.html
You should use Element (https://element.io) instead, which doesn't require your phone number.
The matrix.org server is overloaded and slow, but unlike with Signal (which is centralized), you can choose from many other servers, and still be able to talk to every Matrix user. server list: https://publiclist.anchel.nl/
So I guess Element (matrix) does not store messages (deleting after delivery) and has a sealed sender option?
Of course, taking in mind that I, as a user, cannot verify anything on any server anyways, whether it's on a decentralized network or not.