@seyon @daniel Still not going to work because few people want to use an app they have never heard of, on a server neither they nor their friends have ever heard of, using a server that might be run by some scammer in Nigeria or Russia or China for all they know. And also they absolutely will not pay for such a service when all the better known services are free, and they're not going to set up their own #XMPP server because that's not something that interests them in the slightest, plus there are no really good videos that show how to do it (not that it would make a difference for most people, but it might for a few).
If you are willing to run a server AND be their lifetime technical support, then you might stand a shot, but beware - what was once easy to set up and use can become far more difficult as time goes by. Software authors all seem to have some disease that forces them to make changes to perfectly good and working software that breaks things, or compromises privacy or does some other bad thing. So while running a XMPP server might seem like a fun project today, it may not seem like much fun at all in a few months or years.
Much easier to just use something like #Signal. but in saying that I realize the fact they demand a phone number is a huge drawback. #Teleguard (https://teleguard.com/en) looks like a possible alternative, it does not require a phone number and it looks like the basic features are free but some other features (such as Zoom-like conferencing) cost money, and as I said few people will pay for something they can get free on a larger or better known platform. But it hardly ever gets mentioned so I am wondering if there is some hidden drawback to it.