I had same problem in Kubuntu. nvidia-prime chages /etc/lightdm/lightdm.conf greeter parameter to unity-greeter. This change prevents lightdm starting. To fix it i had to change greeter back to lightdm-kde-greeter.
I had same problem in Kubuntu. nvidia-prime chages /etc/lightdm/ lightdm. conf greeter parameter to unity-greeter. This change prevents lightdm starting. To fix it i had to change greeter back to lightdm- kde-greeter.