Comment 28 for bug 1716857

In a more pure development environment, I can confirm this bug without needing hybrid GPUs, or gdm3.

Just the Nvidia driver and Xorg results in no outputs/monitors detected:

$ xrandr
Screen 0: minimum 8 x 8, current 640 x 480, maximum 16384 x 16384

To work around the problem I need to run Xorg as root. Then I get:

$ xrandr
Screen 0: minimum 8 x 8, current 1920 x 1200, maximum 16384 x 16384
DVI-I-0 disconnected primary (normal left inverted right x axis y axis)
DVI-I-1 disconnected (normal left inverted right x axis y axis)
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 connected 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200 59.95*+ 59.88
   1920x1080 60.00 59.94 50.00 23.98
   1600x1200 60.00
   1280x1024 75.02 60.02
   1280x720 60.00 59.94 50.00
   1152x864 75.00
   1024x768 75.03 60.00
   800x600 75.00 60.32
   720x576 50.00
   720x480 59.94
   640x480 75.00 59.94 59.93

So perhaps gdm3 is sometimes missing whatever /dev/* privileges it needs to start Xorg on Nvidia properly. And perhaps lightdm just always does it right.

Although a solution here in the medium term might lay in gdm3, I would more like to see the Nvidia driver fix this bug. Because I can reproduce it without any *dm. Just the kernel + Nvidia driver + Xorg.