Comment # 40 on bug 95306 from Tom St Denis

[   12.873675] [drm:amdgpu_init [amdgpu]] *ERROR* VGACON disables amdgpu kernel
modesetting.

amdgpu isn't loaded so it's kinda hard to support that config.

Why not blacklist amdgpu and remove your dm/wm from init.  Then ssh in and
modprobe it while running 'dmesg -w'.

That way if your system hangs you might still get some output.