Ok so a few problems, on every network I've tried.

DuckDuckGo: Adding people doesn't seem to work via QR code, at all. And the client gets weird when trying to delete the account.

evil.im: Adder never gets notified that they have been "accepted", so can't view the conversation except via notification.

null.pm: Adding works fine, but OMEMO just stays at yellow exclamation marks.

dismail.de (supposedly has a fully green bar): No QR code adding, no notification of accepted contact request, OMEMO is fucked.

talker.to Basically the same as dismail.de.

So is there an actual server that is reliable and supports the requisite features set to make this a usable experience?

Are these client bugs?

Because otherwise this is going nowhere. I'm sitting next to my mate and cannot actually find a server that allows us to communicate normally.

I'm trying to set up a Jabber prosody server and I think it's working. I have no idea how to test if it is really. I got A/A on the server test thing.

How do they compile a list like this?

https://gultsch.de/compliance_ranked.html

Do they have a suite that I can run against my own server?