Unfortunately even after installing the package, nothing appears … by tapping this command that must be the good it confirms that I am on lightdm ; “cat /etc/X11/default-display-manager” -> /usr/sbin/lightdm
if you are on the beta 18.04 there has been a recent update that has
installed a lightdm or slick greeter settings, which may be available in
other versions than 18.04 but it is available in 18.04, another similar
tool was installed when they used plain lightdm, however I am not sure that
all of the settings work in the settings tool, but some do, you can change
the theme, but it does nothing as I do not think the slick greeter is
really gtk themed if it is the settings tool does nothing to change it, at
least in my experience
I have customized the login screen using a config file, I can provide more info when I get home if you’re interested. That was the easiest way for what I wanted to do.