@coolbeans @newt @ellenor2000 @olmitch AFAIK XCompose has always been a client-side-handled mess, at least I remember it being quite broken on X11 when an Input Method of all the things wasn't used.

And yeah wlroots/sway might be the only one allowing raw xkb configuration files, at the surprise of no one to be honest.

XKB might need a redesign at some point but it's a pretty hard thing to do and I think any kind of replacement is going to end up worse (or being a non-replacement like what's been happening for almost 20+ years on the Desktop Environments side of things).