Just finished the last test from yesterday's recommendations. It appears I
cannot boot with iommu=off as that disables all USB devices, so I can't use a
keyboard and mouse and cannot do anything. I tried the closest working
equivalent I could find, which still froze after 15 minutes from bootup:

cma=0 iommu=soft intel_iommu=off amd_iommu=off

(In reply to iive from comment #27)

Thanks again, I'll be moving to these tests next and posting the results here.