Alright, I went from (patches xkeyboard-config-yr-patch) to (patches (list xkeyboard-config-yr-patch)) and that compiles.
However, I don’t know which package my system is using now and it doesn’t seem to be applied, even though it applies fine from the source code.
But when I look up the package ?I think my system is using? through realpath $(guix build xkeyboard-config) and guix package -I | grep xkeyboard-config it does show the patch applied however.
[edit]
It looks like the patch is nowhere to be seen when I try a guix upgrade.
$ guix upgrade
guix upgrade: error: canonicalize-path: No such file or directory: "xkeyboard-config-yr.patch"