If you have the Nvidia driver installed then it might be called 'Ubuntu' rather than 'Ubuntu on Xorg'. To see such options on the login screen, click your username and before typing your password then click on the icon in the bottom-right corner of the screen.
If you have the Nvidia driver installed then it might be called 'Ubuntu' rather than 'Ubuntu on Xorg'. To see such options on the login screen, click your username and before typing your password then click on the icon in the bottom-right corner of the screen.