Ubuntu 20.04 does not recognize second monitor

I ran into this same issue with nvidia RTX 2060 laptop (MSI GS65). External monitor connected via DisplayPort doesn't show at all through ubuntu settings, but is recognized if I look at nvidia settings. There's a disconnect somewhere.

I downgraded to nvidia-435 driver, and it worked fine. Something didn't get thoroughly vetted/tested with the 440 driver. Just downgrade for now and see if that helps.

I had the same issue: Yesterday I decided to install my new notebook (ThinkPad P72 with NVIDIA GPU).

First I was happy: there were no problem with the NVIDIA GPU when I installed Ubuntu 20.04. I was happy, since I had an issue with this on Ubuntu 18.04 on another notebook: there I had to switch to the default driver in order to be able to install Ubuntu 18.04 on the system at all or the installation suddenly freezed.

But when I booted Ubuntu 20.04 at home and wanted to connect my notebook to the external monitor for convenience reasons, the usual "Windows+P" shortcut did not work, since it could not detect the external monitor. There was also no second monitor when I opened "Settings-->Displays"

My solution was to go back from NVIDIA driver 440 to 435 by clicking "Activities --> Software & Updates --> Additional Drivers". Also a restart was needed such that Ubuntu used the 435 driver version.

Now I can choose the monitor to use with "Windows+P" after start and I am using my external monitor right now :)

So it seems the NVIDIA driver 440 has to be updated to work better with Ubuntu 20.04.

Try this, if not, I'll have my post edited.

Original answer from here.

"I've recently installed nvidia-418 driver on my laptop which uses Ubuntu 18.04. At first the external monitor worked perfectly, but after I switched from power saving mode (sudo prime-select intel) back to performance mode (sudo prime-select nvidia), the second monitor was not detected anymore.

I discovered that prime-select writes a configuration file which causes the problem. It enables the nvidia-drm modeset option. You can simply undo the change made by prime-select by commenting out this option. It will not be reset, because prime-select only writes this file when it does not exist yet."

Open the file in your favorite editor (vim, nano, gedit, etc.).

sudo nano /lib/modprobe.d/nvidia-kms.conf

And comment out the the nvidia-drm modeset option.

# This file was generated by nvidia-prime
# Set value to 0 to disable modesetting
# options nvidia-drm modeset=1

"Hope this also helps you and many others!

ps: It is completely normal that the second monitor is not detected in power saving mode when the connection is part of the nvidia graphics card."