Second monitor not displayed (ubuntu 20.04, Nvidia 455.23.05, Cuda 11.1, ASPEED integrated GPU, 2 dedicated RTX 2080 Ti)

I could not configure my PC to extend the screen to a second monitor by using the HDMI or DisplayPort outputs from the two dedicated RTX 2080 Ti. I am trying to configure it in an Ubuntu 20.04, NVIDIA drivers 455.23.05 and CUDA version 11.1. The first monitor is connected to the VGA output, corresponding to the integrated GPU (ASPEED)

If I run the command “sudo nvidia-xconfig”, and I reboot the system, then the system do not starts. It results in black screen with the following error message:

You can download the nvidia-bug-report generated in this situation here:

In order to be able to start the system again, I had to delete all lines inside the file “/etc/X11/xorg.conf/”, resulting in a blank xorg.conf file. In this situation, I can not visualize the second monitor (just the first, connected to the ASPEED VGA port), and the nvidia-bug-report generated was:

I also found that the “NVIDIA X Server Settings” (nvidia-settings) do not includes the items “X Server Information” and “X Server Display Configuration”, as you can see in the following image:

Do you have any solution to these issues?

Finally, I would ask you if the use of dedicated GPUs affects the performance of these GPUs when using them to train AI neural networks.

Thank you in advance :)