Comment 22 for bug 1632322

Temporary workaround is installing lightdm to get a logon screen and switch back to gdm3 when this bug is fixed.

I am also waiting on this bug to be fixed. I had this problem also a couple of years back.

sudo apt install lightdm

sudo dpkg-reconfigure lightdm

Then choose lightdm. Now you can use a login screen, instead of using auto-logon.