How is login screen set

[Ralf Mardorf]

Hi,

the Ubuntu flavours are using different _display managers_ by default.
What you want to edit is the display manager's _greeter_.

From my Ubuntu 16.04 server install, that came without those things by
default, I added it later, for example

[root at moonstudio weremouse]# ls -l /etc/lightdm/
total 16
drwxr-xr-x 2 root root 4096 Jun 23  2016 lightdm.conf.d
-rw-r--r-- 1 root root 2757 Jun 26  2015 lightdm-gtk-greeter.conf
drwxr-xr-x 2 root root 4096 Jul  7  2016 lightdm-gtk-greeter.conf.d
-rw-r--r-- 1 root root  452 May 18  2015 users.conf

Some quasi parts of the display manager's configuration are usually
provided by the used desktop environment packages or window manager
packages, e.g.

[root at moonstudio weremouse]# ls -l /usr/share/xsessions/
total 8
-rw-r--r-- 1 root root 230 Mar 19  2016 jwm.desktop
-rw-r--r-- 1 root root 198 Jan 24  2018 openbox.desktop

I'm using X, so I can't help with Wayland:

"Some display managers use a separate /usr/share/wayland-sessions/ to
list Wayland-specific sessions." -
https://wiki.archlinux.org/title/Display_manager

Regards,
Ralf