You will need to create an /etc/lightdm/lightdm.conf with these contents: (do this as root)
[SeatDefaults]
autologin-user=<YOUR USER>
autologin-user-timeout=0
user-session=Lubuntu
greeter-session=lightdm-gtk-greeter
You will need to edit the /etc/lightdm/lightdm.conf with these contents: (do this as root)
Remove or comment out the following lines
autologin-user=<YOUR USER>
autologin-user-timeout=0
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