AMD and NVIDIA GPUs together on Ubuntu 20.04

It's not really the answer, but if it helps.

I have both AMD and Nvidia on a laptop I force Nvidia with instruction from https://forums.developer.nvidia.com/t/i-cant-enable-nvidia-gpu-with-nvidia-prime/69899/4

In this file /usr/share/X11/xorg.conf.d/10-nvidia.conf I put:

Option "PrimaryGPU" "true"

And reboot

Steps to install Ubuntu 20 with Nvidia + AMD

1. Install Ubuntu 20.04.2.0 LTS (Focal Fossa) server
2. Once started

   apt-get update && time apt-get dist-upgrade
   

3. Reboot and then install AMD drivers

   wget --referer https://www.amd.com/en/support/kb/release-notes/rn-amdgpu-unified-linux-20-45 https://drivers.amd.com/drivers/ linux / amdgpu-pro-20.45-1188099-ubuntu-20.04.tar.xz
   tar xJf amdgpu-pro-20.45-1188099-ubuntu-20.04.tar.xz </code>
   cd amdgpu-pro-20.45-1188099-ubuntu-20.04
   sudo ./amdgpu-pro-install --opencl=legacy,pal --headless --no-dkms 
   

4. Restart and install Nvidia drivers

   ubuntu-drivers autoinstall
   # Note: check with nvidia-smi
   # If it has not been installed correctly then execute:
   sudo apt install nvidia-driver-455
   

5. Reboot and install clinfo

   apt install clinfo
   

   run clinfo to check that both cards have been detected