Conversations.im has made great progress in making XMPP usable on mobile devices, although its services don't seem ready for public adoption quite yet. There are very few XMPP servers which support the XEPs Conversations does so while federation is theoretically possible, it is not yet a reality.
The new extensions are all public and supported by the two main server implementations, prosody and ejabberd. You can nicely ask your server operator to enable them.
Yep. In addition to that, it’s also FOSS¹ and you aren’t limited to only getting it from the Google Play Store; it’s also distributed² on F-Droid³ too. One thing to note though is that the version of Conversations on F-Droid doesn’t support push notifications, since that functionality uses Google Cloud Notifications.
https://account.conversations.im/