… don’t worry about your hardware Tom … like described above, I debugged the CPU eating kworker process with perf. The dump shows clearly the call of nv50_disp_atomic_commit_tail consuming al the CPU power, which is part of the nouveau kernel module.
And the above mentioned method of downgrading the kernel includes, that new kernels farther are installed and can be tested. If a new kernel appears, install it and reboot. If the error returns reboot again with the downgrade kernel which is saved and selectable in the bootloader. Make it permanent again with: grubby --set-default /boot/vmlinuz-5.8.15-301.fc33.x86_64