Setting only services.xserver.xkb.layout moves the graphical session but
leaves console.useXkbConfig unset, so the virtual-console keymap -- and the
systemd initrd the LUKS passphrase prompt runs in -- fall back to US (seen
on a Latitude 5410: X11 Layout gb, VC Keymap unset, LUKS prompt US).
Default console.useXkbConfig + console.earlySetup + boot.initrd.systemd.enable
distro-wide, so xkb.layout alone reaches the console and the encrypted-disk
prompt. Moved the latter two out of plymouth.nix -- they no longer hinge on
the splash being enabled. All mkDefault: an explicit console.keyMap or a
scripted initrd still wins.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>