On a fresh Ubuntu 20.04 installation, I installed Unity and configured it to use
lightdm in the installation wizard. The login screen looks different, where we now have the option to select the desktop environment to use before logging in.
sudo apt install ubuntu-unity-desktop
I then decided to switch back to the default GNOME desktop by uninstalling Unity. However, the login screen does not go back to the original one that came with the fresh Ubuntu 20.04 installation even after restarting the computer.
sudo apt purge unity-session unity
sudo apt autoremove
sudo apt install ubuntu-session gdm3
How can we restore the original login screen in Ubuntu 20.04?