Reverse PRIME is known not to work with amdgpu. For future reference, we’re investigating what goes wrong with mapping its dma_bufs in internal bug number 2759189. The bug tracker isn’t public, but you can use that number to refer to this issue.
The garbled screen with some reverse PRIME resolutions is being investigated in internal bug number 200627069 and it looks like the problem has been identified and a fix is in progress.