I have configured (in systemsettings) may keybaord to use the layout "German (no dead keys)".  However, when I reboot my system, the wrong keybaord layout is used: It uses the default German keyboard layout, enabling dead keys.

I can "fix" this for the USB keybaord by unplugging and replugging it, but then the internal keyboard of the laptop will keep using the wrong layout.  Alternatively, I can switch the layout back and forth with the keyboard layout status indicator; that will fix things for all keyboards.

But of course, the correct layout should already be applied on login.