I freshly installed ubuntu 20.04 on my laptop after erasing the previous version (18.04) and deleting everything.
When I tried to connect my external monitor via HDMI cable the monitor was not detecting any signal, although it was working fine with the previous Ubuntu 18.04.
I am using an HP ZBook 15 G6 laptop, with "NVIDIA Corporation TU106GLM [Quadro RTX 3000 Mobile / Max-Q]" GPU and nvidia-driver-435 installed.
xrandr is not detecting the display:
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
eDP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
1920x1080 60.03*+ 60.01 59.97 59.96 59.93 40.02
1680x1050 60.00 59.95 59.88
1600x1024 60.17
1400x1050 59.98 60.00
1600x900 59.99 59.94 59.95 59.82
1280x1024 59.95 60.02
1440x900 59.89
1400x900 59.96 59.88
1280x960 60.00 59.99
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 59.97 60.00
1280x720 60.00 59.99 59.86 59.74
1024x768 60.04 60.00 59.95
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 59.96 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 59.94
720x405 59.51 58.99
720x400 59.97
684x384 59.88 59.85
680x384 59.80 59.96
640x400 59.88 59.98 59.96
576x432 60.06
640x360 59.86 59.83 59.84 59.32
640x350 59.84
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
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
I switched to lightdm, and switched back to gdm3, yet both of them did not solve the problem.
Some answers suggested editing the /lib/modprobe.d/nvidia-kms.conf file, and comment the options nvidia-drm modeset=1, But it is not present on my computer. I can only find the nvidia-graphics-drivers.conf file under /lib/modprobe.d.
How may I solve this?
EDIT : I have noticed a strange thing. When I "SUSPEND" my computer and resume later the external monitor is being detected and works normally. But when I restart the problem is same as before.
Best Answer
OK so after a lot of internet scraping and unhelpful solutions, I have gotten it fixed in my case. I am running an AMD 400 series AMD graphics card. What is downloaded automatically in the drivers upon 20.04 installation is not sufficient (this includes the situation when you check the box for install third-party drivers on installation!). Below, I will outline briefly what I did, but since people have different computers with different specs, I can't get too specific without causing future viewers to install the wrong media and mess up their system.
Below is for an AMD system (If you have intel processor, you will do a similar step, but on the intel driver site)
Go to https://www.amd.com/en/support/kb/release-notes/rn-amdgpu-unified-linux-20-20
Select the software that matches your version of ubuntu/RHEL/SLED. For me, version 20.20 for Ubuntu 20.04. (OP this looks like what you will choose, too)
Also look at the download instructions. This outlines the documentation that is important to understand what you are doing!
3A. Briefly, you will download a tar.bz file called amdgpu.blahblahblahb.tar.bz
3B. You will extract it.
3C. You will navigate to it.
3D. You will run the amdgpu-install script in the terminal. I just dragged and dropped it into my terminal and hit enter. I did get a problem here where it wouldn't install at first because there was a driver already partially installed (I think this may have been the automatically installed driver that ubuntu gave us upon installation). To hop around this, I added the keyword uninstall (/.amdgpu-install --uninstall), then re-ran the script again (./amdgpu-install)
Cheers!