Sorry for the late reply on this.
Could you try adding the following kernel parameters (via Grub
by
pressing 'e', then appending the option at the end of the
cmdline):
* nomodeset
and if it doesn't work:
* amd_iommu=pt ivrs_ioapic[32]=00:14.0 iommu=soft
The amd option didn't work, but nomodeset allowed me to get to a
shell,
at which point I could start experimenting with various settings
to see
if I could get a graphical environment. I finally did by switching
over
to the proprietary kernel (which points to a graphical driver
issue with
AMD Navi cards in the libre kernel), but that's obviously less
than ideal.
Still, it means I can finally start using the system in
earnest. Thanks
for all your help!