Further experiments showed that it would be better to remove the stale config file /etc/lightdm/lightdm.conf instead of installing the additional package lightdm-gtk-greeter. Then the much nicer qt version of the login screen is in use and the KDE systemsettings can be used to configure the login screen.
Further experiments showed that it would be better to remove the stale config file /etc/lightdm/ lightdm. conf instead of installing the additional package lightdm- gtk-greeter. Then the much nicer qt version of the login screen is in use and the KDE systemsettings can be used to configure the login screen.