Nvidia – Failed to open Light Display Manager – lightdm issue – switch to sddm

One of the reasons of this error message

Failed to open light display manager

is that the lightdm is really failing and that is not the Nvidia driver or the configs that are behind it.

Solution

Switch to SDDM and rule out if it is a lightdm issue or not.

sudo pacman -S sddm

sudo systemctl enable gdm.service -f

and reboot.