I've had good fortune converting some family and friends to use XMPP.
People always mention fragmentation, and while there is some truth to it, it can be massively minimised by choosing blessed clients and servers for them to use.
In my case, I run my own server, and thoroughly test the clients (especially the onboarding flow) that I expect them to use, so that any question they have, I can help them out with quickly. Since we're all on identically configured servers, it minimises one whole class of incompatibilities.
There is still unfortunately a bit of a usability gap compared to Signal - particularly on the iOS clients. But they have come a long way and are consistently improving.
I'm using Matrix/element. I rather not give my phone number, you see, which is must-have for Signal. I have installed the app in my family's phones, and they were accepting, so all is well. I don't need to communicate through private messaging with anybody else, so who cares if others don't use matrix?
I'm not interested in running servers, in fact, my ISP doesn't allow it anyway. I need something private that doesn't ask for too much info off of me, and that's why my solution was matrix, and not signal.
Why is Session always mentioned ? It's an Australian company, in a land with zero constitutional oversight I'd be more inclined to think its a honeypot then a privavy focused chat app. Anom springs to mind as an example.
The major one that concerns me is who is behind them. Even if we trust that their encryption is not backdoored, there is a lot of information that can be gathered just from the frequency of messages and who they are between.
If it came out that a three letter agency was running one of these networks, it would not suprise me at all.
Yeah but you cant really obfuscate your message destination and timing without using onion routing, and really thats just making it more expensive to compromise and run. That said other things here do make it seem like a honeypot...
Its fully open source though, even the server. Might not be that hard to fork it and let people host their own servers.
Onion routing isnt a foolproof answer either, if the three letter agency runs the entry/exit nodes. There are lots of rumors of tor being compromised.
I wasnt clear in my original comment, but I do trust Signal mostly (naively?), its the other Signal forks/clones that i do not trust at all. So if someone forked Signal and made it self-hostable, that would be interesting, but near impossible for me to trust.
Being open source doesnt mean its not backdoored, see xz. ;)
The difficulty of any non-mainstream chat app is getting other people to use it. On that list, Signal is the most probable to be recognized by people who don't have a particular interest in privacy, so it's more likely to get more people to use it.
besides that, and besides the lack of forward secrecy on matrix and session already mentioned by privacy guides, do some of these alternatives have worse security, privacy, or ux than signal in some way?
Signal has read receipts, reactions and typing indicators. That's 90% of what any messenger needs. It also let's you schedule texts. I do wish it would do reminders and pinch to resize text though.
Matrix also does have a pretty big problem with meta data. By default it stores a ton of meta data (at least the reference server implementation does) and I am not sure if this is even a solvable problem without redesigning the protocol. When opting for an alternative to Signal, XMPP is probably the better choice.