Actually, the Wayland experience for a custom keymap is worse than for the Xserver. If the corresponding symbol file in /usr/share/X11/xkb/symbols cannot be read (permission) then Plasma crashes so badly that we have to reboot the computer using a kernel Ctrl+Alt+Del. After a major upgrade, it is common that a xkb update breaks the custom keymap. In this case, Kwin only reports errors in /var/log/message, doesn't show any UI error message and uses the next keymap as a fallback. KDE settings experience is also bad : - It resets the keymap list when we disable it - We have to change the keymap list order to make fix and try until it works as expected - It reports any errors On Linux, I would expect a command line and UI that reports a comprehensive error and a fallback to an internal US keymap or a clean session abort.