Before upgrading to Ubuntu 16.04 from 14.04 I used to log into GNOME-flashback desktop session from GDM login prompt. After upgrading to Ubuntu 16.04 I had to remove GDM(along with nvidia proprietary drivers etc.) as it never starts(gets stuck at systemd prompt) and installed LightDM again. It was going on without further problem since then until today I tried to change the session to GNOME-shell from LightDM.
I clicked the desktop session chooser button at top-right of the little login box provided by LightDM greeter screen and it gave me a blank box instead of a list of desktop sessions. I managed to bring back the password prompt by clicking on hostname on the top left of the screen. But now I can only log into GNOME shell.
The steps I tried without success
Listing out possible desktop environments
$ ls /usr/share/xsessions/ gnome.desktop gnome-flashback-metacity.desktop gnome-flashback-compiz.desktop ubuntu.desktop
manually creating a (possibly deprecated)
/etc/lightdm/lightdm.confwith following content
and subsequently after it didn't work
~/.dmrc(which was present in system before this problem)
[Desktop] Session=gnome-classic Language=en_US.UTF-8
So now I'm stuck with GNOME shell as the only desktop environment. I want to go back to GNOME classic session and want to be able to switch between desktop environments when needed. Any help on this?