I believe my question says what I am trying to achieve.
Steps I tried to make gdm my default display manager:
sudo dpkg-reconfigurethan select gdm as my default.Edit
/etc/X11/default-display-managerand change its content to/usr/sbin/gdm
After the above two steps I logged out myself and after that when I see my login screen it still shows lightdm as my display manager.
What am I doing wrong here.?