I have the same problem on two computers.
Latest kernel pushed in the updates - linux-headers-5.4.56-generic breaks AMDGPU drivers compilation.
amdgpu-dkms failed each time. If i rollback to previous kernel, it compiles properly.
Am i missing something? Does AMDGPU not support this kernel version?
Good news is even AMD has acknowledged the issue, they even added the problem in their release notes of their latest GNU/Linux drivers, they advised to do not upgrade to this kernel as AMDGPU needs amdgpu-dkms in order to work properly. They are working with the GNU/Linux Ubuntu devs to understand what happened and hopefully fix the issue in the near future. More info here in the known issues section: https://www.amd.com/en/support/kb/release-notes/rn-amdgpu-unified-linux-20-45
had problems with this kernel version as well on Ubuntu 20.04.1 today, especifically related to notebook's lid triggered suspension, just issued here: Ubuntu 20.04 does not wake up properly after lid is closed with Linux Kernel 5.4.0.56 (Report an issue)
Hope this get worked out soon. For now I would recommend you to use version 5.4.0.54 for the kernel, it worked for me at least. Just a note, my problem ocurred on a laptop with Intel integrated graphics card.
