So is there a list of "Modern XMPP" compliant clients, server software and hosts that I can compare the experience of to the Matrix ecosystem?

I was a pretty big user of XMPP with Pidgin on first GTalk and then later DDG's server back in the day, because that's certainly not comparable. I'd really like an open chat solution to succeed, but from where I sit "Can I convince any of my friend groups to move from discord to this?", Matrix is substantially in the lead.

I'd suggest taking a look at Movim: https://movim.eu/

It takes an appropriately set up xmpp server and essentially reproduces a social network. Microblogs, groups, and chat. Implements OMEMO and the like if memory serves. It is a great platform and just as compelling as Discord IMO.

> It takes an appropriately set up xmpp server and essentially reproduces a social network. Microblogs, groups,

This to me is missing the point - I don't even like Discord's attempts to expand into social networking, and Skype's attempts at doing the same was the impetus for many of my friend groups to move to Discord. What's needed is something that does group chats and PMs effectively.

XMPP has done that for what, a couple of decades now. MUC and PM are very much solved problems. Have I missed something?

No, this discussion isn't a comparison of implementations it's a question/discussion of why "the latest implementation" is tied to a new extensible protocol instead of a new baseline of the existing extensible protocol. There may well be reasons but "the first implementation was on the new protocol" explains the current state not how things got there.

That's pretty neat. Are there any compliant clients? If I google the XEP you linked I can't find anything but mailing lists and posts talking about it.

We're working on surfacing this information. It's hard keeping track of a diverse and evolving ecosystem - it's been attempted in the past (years ago), but manually keeping things up to date didn't work out because the info quickly got stale. More recently we've built tooling so that projects can document what they support in a machine-readable format on their site or in their repo. Most active XMPP projects are already on board with this, and we should see some nice front ends to it live soon.

The ultimate goal is an easy user-facing site with a shortlist of the clients that implement the expected modern features, alongside a longer filterable list for people who don't necessarily care about certain features (calls, for example, which are generally not expected in TUI apps).