linux@localhost:~> xdg-su -c “/usr/bin/start-install.sh”
No X authentication info set for display “:1”
Don’t need password!!
This is a bug.
Or rather a missing feature.
It’s currently not possible to run graphical applications as root in a Wayland user session via xdg-su or similar, out of the box at least.
See 955101 – YaST2 doesn't start under Gnome / Wayland for a “workaround”.