I've been inspecting this topic quite a lot and I'm a little confused now. So, we have reasons not to use Signal, reasons not to use Matrix, there were also some claims about Session being a fraught. Briar is mostly activists related (not very suitable for daily use), XMPP lacks good clients and suffers from fragmentation of protocol standards implementation, SimpleX is too feature-incomplete (no UnifiedPush support, big battery drain on Android, very decent desktop client without any message sync). I can't say a lot about Threema or Wire, as I'm not very familiar with them.
So, my question is — is there any good private messenger at all? What do you think is the most acceptable option?
EDIT: In addition to my post:
All messengers have their flaws, I'm well aware of that. I was interested in hearing users' opinions regarding these shortcomings, not in finding the perfect messenger. I may have worded my thoughts incorrectly, sorry for that.
Almost all those can be self-hosted, and built from source, so matrix, xmpp, simplex, are fine. Don't use anything that's uses a centralized server in a five eyes country, like signal or threema.
How is Threema in a five eyes country?
I mean, sure, only the clients are open source. Don't use it for that.