In my case, I was able to fix the issue without removing lightdm - I discovered, that for some reason (I never made according changes, I am 100% sure)
/etc/lightdm/lightdm.conf
contained
[SeatDefaults] greeter-session=unity-greeter user-session=ubuntu autologin-user=<my_user>
I commented out the last line in #autologin-user=<my_user>
and that solved the issue with the missing rights for me.
Nota bene: Autologin was NOT active - I had to login with password, and I NEVER selected to autologin as we have a multi-user desktop here at home.
In my case, I was able to fix the issue without removing lightdm - I discovered, that for some reason (I never made according changes, I am 100% sure)
/etc/lightdm/ lightdm. conf
contained
[SeatDefaults] session= unity-greeter user=<my_ user>
greeter-
user-session=ubuntu
autologin-
I commented out the last line in user=<my_ user>
#autologin-
and that solved the issue with the missing rights for me.
Nota bene:
Autologin was NOT active - I had to login with password, and I NEVER selected to autologin as we have a multi-user desktop here at home.