the last test to do is to test the onboard Display Port video port after removing nvidia card, in case the integrated HDMI port is broken.  if no DP video either, this xps 8920 motherboard igpu is likely defective and you may only get video from a discrete video card.
I would like to remove the Nvidia card that was ordered with system and get the onboard graphics HDMI output to run a monitor?
XPS 8920 - Remove added graphics card and use only onboard graphics