How to completely reinstall lightdm

[again?]

Is lightdm still installed?

apt policy lightdm

Not familiar with loki.
Doesn't it have a pantheon-greeter for lightdm?
Did you install lightdm-webkit-greeter in an effort to change the greeter?

[again?]

I'm off to bed so I'll leave you with some info.
https://www.freedesktop.org/wiki/Software/LightDM/
https://wiki.archlinux.org/index.php/LightDM

I would delete /etc/lightdm/lightdm.conf which is a sort of master admin config that overrides settings in /usr/share/lightdm/lightdm.conf.d

You greeter-session used will then be what's shown by configs in /usr/share/lightdm/lightdm.conf.d, higher numbered files taking precedence.
Your "lightdm --show-config" output shows that /usr/share/lightdm/lightdm.conf.d/60-lightdm-gtk-greeter.conf will now be the source for your lightdm config.

Try to use lightdm again...

sudo rm /etc/lightdm/lightdm.conf

sudo apt install lightdm lightdm-gtk-greeter
sudo dpkg-reconfigure lightdm

[mattdiamond]

Still not working I eventually switched to windows back becuase of software compatibility... Thanks!!