Comment 1 for bug 1998866

The issue was resolved using the tip found at https://askubuntu.com/questions/67764/how-to-remove-and-reinstall-gnome-3 by Esmaeil MIRZAEE who suggested purging gnome-shell and reinstalling it. Just "remove" wasn't enough.

"1 and 2 provide a simple step by step guide to install Gnome on Ubuntu. However, for the sake of completeness, first of all, remove the current Gnome by apt purge gnome-shell. And then reinstall the following packages, apt install gnome -shell ubuntu-gnome-desktop.

Finally, one more thing is to choose the default graphical interface, for instance, when you are hosting LXDE and Gnome-3 simultaneously on your PC, it will ask for gdm3 V lightdm.

May 9, 2018 at 21:36
Esmaeil MIRZAEE"