From: https://askubuntu.com/questions/1152547/how-to-change-the-ubuntu-19-04-gdm3-cursor-theme:
Add at end of file /etc/gdm3/greeter.dconf-defaults
:
# Theming options
# ===============
[org/gnome/desktop/interface]
cursor-theme='CURSOR_NAME'
#cursor-size=35
#[org/gnome/desktop/peripherals/mouse]
#speed=-0.8
From: https://askubuntu.com/questions/11738/force-gdm-login-screen-to-the-primary-monitor:
sudo cp ~/.config/monitors.xml /var/lib/gdm3/.config/