As someone who has worked extensively with XMPP in the last ~6 years let me tell you that it works fine with network hopping, multiple devices and everything else you'd come to expect from a modern IM experience in the likes of WhatsApp and Signal.
I have written a lengthy article in 2016 in the state of mobile XMPP: https://gultsch.de/xmpp_2016.html
The situation has only improved from there.