The main goal of switching LightDM to slick-greeter is to ease
enabling/disabling autologin. With "lightdm-settings" installed, there
is an administration/settings GUI "Login Window" available that allows
among others to configure autologin. Contrary to its general purpose
name, it works on LightDM greeter "slick-greeter" only.

[ci:skip-build]: already built successfully in CI