Yeah but XMPP sounds so techy you know... /s

the trick is to not mention XMPP to the end users. if they dig deep in the app settings they can find it out, but otherwise all that end users need to know is just, download the app named conversations, and use this domain and username. the domain could likely be hidden from them by deep linking, and sending the link in a company email. then they just need to log in as anywhere else.