You can find here a nice comparison sheet of different “secure” messengers. Very interesting read for me!
Threema is really good. I believe they should open things up a little bit. Esp. the clients.
That seems to be two years old, and is at least not correct for current Riot.
I’m mostly interested in Messengers that also do secure video calls. So far, Signal has been working very elegantly, but is getting controversial in its recent updates.
Also I would like to have some kind of control regarding which servers are used to store/convey messages and user details. In that respect I like the way aTalk works, using public XMPP servers like hot-chilli.eu, which does not even require a phone no. or SIM. It is not currently available to Apple users though.
There also seem to be messengers that can do without a server (Briar?), but that is maybe a level of privacy above what is needed by the casual user.
I am testing https://getsession.org/ lately, which is a fork of signal but is build on top of onion routing and Dynamically generated IDs (like briar). They plan to migrate later to the LokiNet approach (since session is a loki project).
This should fix nearly all the red marked problems with Signal. And my first tests are really promising!