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.

I encountered the same issue on my laptop dual card (Dell G5 5587) Ubuntu 20.04.

In my case the issue was snapd. I have purged and disabled snapd before (that's the fault).

The issue appear when I use NVIDIA compatible drivers Ex. 435,440,450 with prime on demand or performance mode

That's the issue, because ubuntu 20.04 use combined packages (classical deb and snap)

Solution in my case was the following:

sudo apt install snapd
sudo snap install snap-store
sudo reboot

At the end in Settings-Display all the options appear also for the second display (Join, Mirror,Single) and NVidia works again