hrthuThere should be something like meta-XEPs for #XMPP. One of the problems w/ XMPP is the uneven support for #XEPs across many diverse clients and servers. If there was an umbrella that said any client/server that targets desktop chat should have XEP X, Y, and Z. While one that supports mobile should have A, B, and C. And a client suporting #videochat should R1, R2, and R3.
Goffi@hrthu that's the point of compliance suite (https://xmpp.org/extensions/xep-0412.html).
#XMPP should not be seen as a single protocol "for IM", but as a coordination of coherent protocols, see my FOSDEM talk about it: https://mirror.as35701.net/video.fosdem.org/2019/H.1309/xmpp_beyond_im.webm
@Goffi Thanks, I was not aware of this (though the distinction between "core" and "advanced" seems rather simplistic. Either way, it still seems that clients/servers choose to support different XEPs. Either that or 'core complience' is not enough to have a modern desktop client do what people now expect of a chat client.