https://bugs.freedesktop.org/show_bug.cgi?id=108307
--- Comment #3 from Samantha McVey samantham@posteo.net --- I was able to get something on the screen when I added "pci=noacpi" (this was without blacklisting amdgpu).
[Firmware Bug]: AMD-Vi: No southbridge IOAPIC fonud AMD-Vi: Disabling interrupt remapping platform USBC000:00 failed to claim resource 0: [mem ...] acpi USBC000:00: platform device creation failed: -16 AMD-Vi: Unable to write to IOMMU perf counter. ...
I uploaded an attachment which shows the full output (I only typed out the first several lines).
I might be able to bisect if needed. Does the image I uploaded show you anything useful?