This is caused by the null value of picture-uri in gsettings-desktop-schemas: - https://build.opensuse.org/request/show/825300 If we set a true uri to it, the default theme of gdm greeter will be changed. I will look into it. ------ Current workaround for this error: - Disable gnome-shell-fate324570-Make-GDM-background-image-configurable.patch or - Set a true value for `org.gnome.desktop.background.lockdialog picture-uri`