Comment 13 for bug 1771185

I have basically the same problem. I was using 18.04LTS on a HP ZBook15 laptop and also wanted to connect an external monitor by using the HDMI interface. I have 2 graphics cards intel(i915) + NVidia(390drivers), and whatever I chose in prime-select/Nvidia-settings, the external monitor did not work. 'xrandr' always listed the HDMI port as disconnected, which was not true of course. I also tried using different HDMI cables due to stackoverflow suggestions, but this didn't solve the issue. Then, I updated to 18.10, which I still use now, hoping there would be an improvement, but nothing changed. The monitor is still not working, "xrandr" still says that the monitor is disconnected.

Would really be great if this could be solved. Hoping for the best. Thanks!

xrandr output:
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767
eDP1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 340mm x 190mm
   1920x1080 60.00*+ 59.93 40.00
   1680x1050 59.95 59.88
   1600x1024 60.17
   1400x1050 59.98
   1600x900 60.00 59.95 59.82
   1280x1024 60.02
   1440x900 59.89
   1400x900 59.96 59.88
   1280x960 60.00
   1368x768 60.00 59.88 59.85
   1360x768 59.80 59.96
   1280x800 59.81 59.91
   1152x864 60.00
   1280x720 59.86 60.00 59.74
   1024x768 60.00
   1024x576 60.00 59.90 59.82
   960x540 60.00 59.63 59.82
   800x600 60.32 56.25
   864x486 60.00 59.92 59.57
   640x480 59.94
   720x405 59.51 60.00 58.99
   640x360 59.84 59.32 60.00
DP1 disconnected (normal left inverted right x axis y axis)
DP2 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)