I was having the exact same problem. (roughly same specification as yours).
I finally got mine fixed.
A warning to anyone reading this. There is a high probability there is a newer kernel that is compatible with the drivers. This is a functional fix and probably not a perfect one. Anyone with more intimate knowledge of kernel + amdgpu is welcome to contribute a better answer.
You need to download, extract and install the 20.50 amdgpu driver.
This is the link I used:
https://drivers.amd.com/drivers/linux/amdgpu-pro-20.50-1234664-ubuntu-20.04.tar.xz
extract and run:
tar -xf amdgpu-pro-20.50-1234664-ubuntu-20.04.tar.xz
cd amdgpu-pro-20.50-1234664-ubuntu-20.04
./amdgpu-install
Then you need to deploy a specific kernel: (5.4.0-96-generic is working for me)
sudo apt-get install linux-image-5.4.0-96-generic linux-modules-5.4.0-96-generic linux-modules-extra-5.4.0-96-generic linux-headers-5.4.0-96-generic
My laptop also has an nvidia GPU. Install these if needed:
sudo apt-get install linux-modules-nvidia-470-5.4.0-96-generic linux-objects-nvidia-470-5.4.0-96-generic linux-signatures-nvidia-5.4.0-96-generic
then reboot
sudo reboot
after reboot, confirm that kernel version was loaded
uname -r
I changed my grub to allow selecting the kernel at boot time. If uname -r returns wrong kernel version, you may need to do the same or change your config to use this specific kernel. I'm not going to include grub config instructions here, but its a simple modification to /etc/default/grub
For reference - this fix is based off information found here: https://www.amd.com/en/support/kb/release-notes/rn-amdgpu-unified-linux-20-45
Hope this helps someone.
