Created attachment 143957 [details]
Dmesg output from an affected kernel

Here is the issue, you can see
[    1.335096] [drm:dc_link_detect [amdgpu]] *ERROR* No EDID read.

Which is about where the display turns into fruit salad.
Please let me know if I can submit any more debug info that would assist! I am
very much in need of running a newer kernel.