Persuading a friend to use Jabber

[Mæstro]

This is a sequel to my earlier one about leaving Discord; a large change in my conditions which solves one of my original problems justifies a new post after my understanding of netiquette. I am happy to report that I have got my XMPP account working again, simply by using Pidgin instead of Gajim or Psi, and learnt that ChatSecure is recommended as an iOS client. (I would be grateful if any iPhone users here could tell me in more detail about how smoothly it works.) Hence, my remaining problem is now rather social than technical. How can I convince my iPhone-using friend, who is apathetic about privacy matters, to download ChatSecure, create a Jabber account and use it to communicate with me instead of Discord? He is busy this weekend, and I happened to suffer one of my worse panic attacks after being bullied online yesterday, so I realise that I should wait at least a few days. When and how do I go about this?

I should also mention that I also preside over another chatroom for friends with five other users, three of whom are active, which, for simplicity, I did not discuss in the original. All are Windows users, but only one was able to figure out how to use Gajim. Advice on how to ease a transition of that group chat onto Jabber would also be welcome, but I realise progress is incremental.