I use another keyboard layout in the desktop, but I can’t switch to it in login screen.
This really isn’t my area of understanding - but a quick look around - this looks promising
So we are using on 26.04 SDDM in its X11 mode - so procedures such as above will still apply (hopefully). Let us know - a step by step guide would be very useful for the community in the future.
Why is X11 mode used? There should be some list of possible codes somewhere with explanations.
During the development cycle we (the team) were not convinced we could get SDDM to work purely under wayland mode - we were seeing things like black screens, long startup times and other issues. We think it was an issue that we were trying to use both labwc for SDDM and labwc for the desktop manager. Using weston seemed to work, but it suffered from long startup times. In Roadmap to Ubuntu Budgie 26.10 there is a goal to relook at this area.
probably this ISO 3166-1 alpha-2 - Wikipedia