Install gir1.2-gdm-1.0 by entering the following commands in the terminal:
sudo apt update sudo apt install gir1.2-gdm-1.0
Description:
GObject introspection data for the GNOME Display Manager
GDM provides the equivalent of a "login:" prompt for X displays: it asks for a login and starts graphical sessions. . It supports multiple seats and switching between multiple users. . The greeter is based on the GNOME libraries and applications, and its look and design are the same as those of a GNOME session. . This package contains introspection data for the GNOME Display Manager.
Version: 3.28.0-0ubuntu1
Section: introspection