Is there anything more secure than signal that is widely used? Maybe something that doesn’t leak metadata or require a phone number?
XMPP/Jabber with OMEMO encryption, it runs on federating servers.
Session is a fork of signal that doesn't require phone numbers, there's some cryptocurrency something or other in there I don't quite get, but I don't believe you need it to send messages.
There's Tox, another p2p sort of thing.
Then there's threema, wire, and a bunch of others im not all that familiar with.