@debacle @frankie I don't even mention setting up own server. When we are talking about communication software, it should be easily accessible, without requirements of solemn wows, degree in computer sciences or even long troubleshooting, otherwise the audience will be marginal, if any.
1. One need to get a client. On mobile it would be most probably #Conversations or some its forks of different degree of weirdness. Conversations requires either to pay them immediately or use #Fdroid. It is not bad to pay or donate them (though I am not happy about giving google my card) but it raises the entrance limit immediately. On desktop, one would have to mess up with a bunch of clients, from which only #Gajim and #Dino seem to be more or less modern (and quite probably one will need to install cutting-edge version from flatpak or whatever).
2. Well, then server. Well, there are reasonable, advice or research is necessary.
3. Troubleshooting and fine mistakes. E.g. #Conversations fails to ask microphone permission when somebody calls in, it just throws error. Yes, it is minor issue, but how many people will say "it doesn't work, it is buggy, why should I?" (recall, on that point the potential new user has already made a lot of research and possibly even paid some money). Again, #Conversations follow some weird barely understandable for me ritual on adding new contacts, I couldn't just add a contact and write to it.
Just to conclude, #xmpp is not a smooth experience for any non-geek.