Ubuntu 18.04.3 blank screen at startup with 430 drivers and GTX 960

Looks like you ran into a driver bug with 430.50 where the gpu thinks it has no outputs. Try adding the graphics ppa and update to 440. Alternatively, run

grep nvidia /etc/modprobe.d/* /lib/modprobe.d/*

to find a file containing

options nvidia-drm modeset=1

and change 1 to 0
then run

sudo update-initramfs -u

and reboot.