It also wasn't difficult to set up your own server and bring your own domain, resulting in an easy to remember vanity handle like [email protected]. I hosted both prosody and ejabberd for years for friends and family, and it was orders of magnitude easier than self-hosting a mail server. Sadly, eventually everyone moved to proprietary platforms because file sending worked badly in those days, and mobile XMPP clients were simply terrible (no push notifications and such).

This is why I use my Matrix bridges. XMPP has bridges too, of course (that's where the Matrix bridges were inspired by) but it seems the "up and coming" status of Matrix helps the bridges be maintained better.

FWIW, the EU has passed the Digital Markers Act which requires big tech companies to open up their platform. It'll take a while before it takes effect, but unless Apple, Google, Meta and all others are going the very expensive "fine me and we'll see what happens" route, we should soon see movement towards an environment where different apps can talk to each other again.

The tech industry being what it is, there is no real standard for interoperability yet, though there is an IETF taskforce working on setting up a standard companies may follow: https://datatracker.ietf.org/wg/mimi/about/

This, critically, considers encrypted messages in a standard way so that we don't lose E2EE in the process.

Let's hope this ends up being good, I can see it taking twenty years and at some point standardizing a backend into the encryption :(