I have exactly the same issue, but on kernel 5.14. I had thought it was due to the GPU drivers not loading properly, but on closer inspection, it appears to be because the monitor is not being detected. On kernel 5.10 it’s detected as “Laptop, eDP”, on 5.14 it’s just default.
Tried upgrading amdgpu/amdgpu-pro drivers (pcie errors in dmesg stating ‘no firmware for amd pcie’ or something to that effect) both through the official AMD ddl, and apt.
No go!
I believe this co-incited with the recent kernel update. Perhaps drivers not compatible with kernel.
There was also an attempt to re-install/install mesa drivers. No fix there either. Definitely a firmware issue, as noted. What that could be is beyond my pay grade.