Why can‘t I use the VGA port of my Lenovo W530 Laptop under Xubuntu 18.04?

I have a Lenovo W530 laptop and it runs Xubuntu 18.04.4 LTS currently with kernel 5.3.0-40-generic x86_64. xrandr has version 1.5.0 and the version of RandR is 1.5.

My problem: I can’t use an external screen attached through the VGA port – neither when it is connected directly to the laptop outside of the docking station nor when it is connected to the VGA port of the docking station when the laptop is seated in it. However, under Windows 10, I can use the external screen in both situations. (Under Windows, the VGA port of the laptop itself does not work properly when the laptop is in the docking station. That does not prevent using the VGA port completely like under Xubuntu 18.04). - If I remember right, the VGA port has worked before uner Xubuntu 16.04, but I have no chance to check that right now.

Under Windows 10 I can use a second screen attached to the VGA port. It is even possible to control three screens by the W530 laptop: the builtin laptop screen, another screen attached through VGA and yet another screen attached through DP (with an adapter DP1-HDMI). In this situation, the builtin laptop screen is controlled by the Intel HD Graphics 4000, the other two screens are controlled by the NVIDIA Quadro K1000M Version 80.7.32.0.f, according to Windows.

The integrated NVIDIA Graphics of the computer is activated in the BIOS. There is a file /usr/share/X11/xorg.conf.d/11-nvidia-prime.conf and its content is

# DO NOT EDIT. AUTOMATICALLY GENERATED BY gpu-manager

Section "OutputClass"
  Identifier "Nvidia Prime"
  MatchDriver "nvidia-drm"
  Driver "nvidia"
  Option "AllowEmptyInitialConfiguration"
  Option "IgnoreDisplayDevices" "CRT"
  Option "PrimaryGPU" "Yes"
  ModulePath "/x86_64-linux-gnu/nvidia/xorg"
EndSection

One hint I found when looking for other solutions, was to put a # in front of the line

Option "IgnoreDisplayDevices" "CRT"

to deactivate it. I did that although I saw the warning at the beginning of the file. This hint did not work. When I looked at this file later, I saw that the # had vanished, so probably it did not survive when I made my test and perhaps it had already gone at my test. The warning at the beginning of the file seems to be fully justified.

lscpi tells me:

a@v:~$  lspci | grep -i vga
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics 
Controller (rev 09)
01:00.0 VGA compatible controller: NVIDIA Corporation GK107GLM [Quadro K1000M] (rev a1)
a@v:~$

xrandr tells me:

a@v:~$ xrandr --prop Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 16384 x 16384 LVDS-0 disconnected (normal left inverted right x axis y axis) CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0 BorderDimensions: 4 supported: 4 Border: 0 0 0 0 range: (0, 65535) SignalFormat: LVDS supported: LVDS ConnectorType: Panel ConnectorNumber: 0 _ConnectorLocation: 0 non-desktop: 0 supported: 0, 1 DP-0 disconnected (normal left inverted right x axis y axis) CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0 BorderDimensions: 4 supported: 4 Border: 0 0 0 0 range: (0, 65535) SignalFormat: TMDS supported: TMDS ConnectorType: DisplayPort ConnectorNumber: 2 _ConnectorLocation: 2 non-desktop: 0 supported: 0, 1 DP-1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 698mm x 392mm CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0 EDID: 00ffffffffffff0034a996a201010101 00180103808048780adaffa3584aa229 17494b21080031404540614081800101 010101010101023a80d072382d40102c 4580ba882100001e023a801871382d40 582c4500ba882100001e000000fc0050 616e61736f6e69632d54560a000000fd 00173d0f440f000a202020202020015a 020322f24d9f90140520212213041203 16072309070168030c001000b8260fe2 004b011d80d0721c1620102c2580ba88 2100009e011d8018711c1620582c2500 ba882100009e011d00bc52d01e20b828 5540ba882100001e662156aa51001e30 468f3300ba882100001e000000000000 000000000000000000000000000000bb BorderDimensions: 4 supported: 4 Border: 0 0 0 0 range: (0, 65535) SignalFormat: TMDS supported: TMDS ConnectorType: DisplayPort ConnectorNumber: 3 _ConnectorLocation: 3 non-desktop: 0 supported: 0, 1 1920x1080 50.00*+ 60.00 59.94 29.97 25.00 23.98 60.05 60.00 50.04 1366x768 59.79 1280x1024 60.02 1280x720 59.94 50.00 1024x768 60.00 800x600 60.32 720x576 50.00 720x480 59.94 640x480 59.95 59.94 DP-2 disconnected (normal left inverted right x axis y axis) CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0 BorderDimensions: 4 supported: 4 Border: 0 0 0 0 range: (0, 65535) SignalFormat: TMDS supported: TMDS ConnectorType: DisplayPort ConnectorNumber: 4 _ConnectorLocation: 4 non-desktop: 0 supported: 0, 1 DP-3 disconnected (normal left inverted right x axis y axis) CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0 BorderDimensions: 4 supported: 4 Border: 0 0 0 0 range: (0, 65535) SignalFormat: DisplayPort supported: DisplayPort ConnectorType: DisplayPort ConnectorNumber: 2 _ConnectorLocation: 2 non-desktop: 0 supported: 0, 1 DP-4 disconnected (normal left inverted right x axis y axis) CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0 BorderDimensions: 4 supported: 4 Border: 0 0 0 0 range: (0, 65535) SignalFormat: DisplayPort supported: DisplayPort ConnectorType: DisplayPort ConnectorNumber: 3 _ConnectorLocation: 3 non-desktop: 0 supported: 0, 1 DP-5 disconnected (normal left inverted right x axis y axis) CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0 BorderDimensions: 4 supported: 4 Border: 0 0 0 0 range: (0, 65535) SignalFormat: DisplayPort supported: DisplayPort ConnectorType: DisplayPort ConnectorNumber: 4 _ConnectorLocation: 4 non-desktop: 0 supported: 0, 1 LVDS-1-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 193mm EDID: 00ffffffffffff0030aeb24000000000 0113010380221378ea2135ad5037aa24 11505400000001010101010101010101 0101010101014c368082703832403c30 aa0058c1100000183f2d808270383240 3c30aa0058c1100000180000000f00d1 0932d109281b190006af5634000000fe 004231353648573031205634200a00d6 PRIME Synchronization: 0 supported: 0, 1 scaling mode: Full aspect supported: Full, Center, Full aspect link-status: Good supported: Good, Bad CONNECTOR_ID: 67 supported: 67 non-desktop: 0 range: (0, 1) 1920x1080 60.00*+ 59.97 59.96 59.93 50.00 1680x1050 59.95 59.88 1600x1024 60.17 1400x1050 59.98 1600x900 59.99 59.94 59.95 59.82 1280x1024 60.02 1440x900 59.89 1400x900 59.96 59.88 1280x960 60.00 1440x810 60.00 59.97 1368x768 59.88 59.85 1360x768 59.80 59.96 1280x800 59.99 59.97 59.81 59.91 1152x864 60.00 1280x720 60.00 59.99 59.86 59.74 960x720 60.00 928x696 60.05 896x672 60.01 1024x576 59.95 59.96 59.90 59.82 960x600 59.93 60.00 960x540 59.96 59.99 59.63 59.82 800x600 60.00 60.32 56.25 840x525 60.01 59.88 864x486 59.92 59.57 800x512 60.17 700x525 59.98 800x450 59.95 59.82 640x512 60.02 720x450 59.89 700x450 59.96 59.88 640x480 60.00 59.94 720x405 59.51 58.99 684x384 59.88 59.85 680x384 59.80 59.96 640x400 59.88 59.98 576x432 60.06 640x360 59.86 59.83 59.84 59.32 512x384 60.00 512x288 60.00 59.92 480x270 59.63 59.82 400x300 60.32 56.34 432x243 59.92 59.57 320x240 60.05 360x202 59.51 59.13 320x180 59.84 59.32 VGA-1-1 disconnected (normal left inverted right x axis y axis) PRIME Synchronization: 1 supported: 0, 1 link-status: Good supported: Good, Bad CONNECTOR_ID: 71 supported: 71 non-desktop: 0 range: (0, 1) 1280x1024 (0x52) 108.000MHz +HSync +VSync h: width 1280 start 1328 end 1440 total 1688 skew 0 clock 63.98KHz v: height 1024 start 1025 end 1028 total 1066 clock 60.02Hz 1024x768 (0x67) 65.000MHz -HSync -VSync h: width 1024 start 1048 end 1184 total 1344 skew 0 clock 48.36KHz v: height 768 start 771 end 777 total 806 clock 60.00Hz 800x600 (0x76) 40.000MHz +HSync +VSync h: width 800 start 840 end 968 total 1056 skew 0 clock 37.88KHz v: height 600 start 601 end 605 total 628 clock 60.32Hz 640x480 (0x85) 25.175MHz -HSync -VSync h: width 640 start 656 end 752 total 800 skew 0 clock 31.47KHz v: height 480 start 490 end 492 total 525 clock 59.94Hz a@v:~$

i.e. it sees the internal screen and the one connected through DP1 but it sees the VGA-1-1 disconnected. Despite of that, it detects the VGA screen's supported resolutions. That’s really strange. Sometimes (e.g. when I start the computer without the other screen connected through DP1), it is also found VGA-1-1 disconnected, but then the lines with the possible screen resolutions of it are missing.

When looking at the screen settings under Xubuntu in the GUI, it dos not offer me the screen which is connected by VGA. The same holds for the NVIDIA X Server Settings app.

The LED on the VGA screen‘s power switch remains yellow. Normally it turns green when Sync signals are seen by the VGA screen's electronics.

Why does VGA-1-1 appear as disconnected although it is connected and the screen is powered on?

What‘s necessary to use the VGA port e.g. for a projector under Xubuntu?