Hello ! I want to add a little more evidence, that the problem stems from lightdm.
My first message contains the error output, which some perl gives, when you create a virtual machine (LCX) via lxc-create. This is done in a console, which, in my case, was mostly the xfce4-terminal. I tried "konsole" too, with the same result. If you: >echo $LANG en_US.utf8 this is the wrong case. If one does the same inside a ssh session, everythings is fine (you'll get uppercase). In the ui session, if one exports all (three) neccesary variables and run the lxc-create again, it works properly. But in this one console only. Best regards, Manfred