Then you can do sudo apt install ubuntu-desktop to get an Ubuntu option at the login screen with this GUI. See https://askubuntu.com/a/65108/158442
– muruMar 06 '18 at 03:39
In your login screen there will be an icon to the right of the username. Click it and you should get a dropdown, like http://1.bp.blogspot.com/-Y63m1CMK6Eo/TtX4QtJykoI/AAAAAAAAB9I/dsXTNuE-baI/s1600/login-dropdown-menu-lightdm.png
– muruMar 06 '18 at 03:49
can't I do that by terminal? I can't find that menu in my gui. There is no such menu.
– creatorMar 06 '18 at 04:52
sudo apt install ubuntu-desktop
to get an Ubuntu option at the login screen with this GUI. See https://askubuntu.com/a/65108/158442 – muru Mar 06 '18 at 03:39