So for what it's worth prior to this snafu my machine was running in SATA AHCI mode. Having since encountered this error I've reformatted my machine and reconfigured SATA AHCI -> SATA RAID and enabled NVMe RAID so that in the event that Microsoft sends down RAID driver updates again it doesn't break my install /shrug.
To make these changes, get into the BIOS (Hold Delete on boot) , go to Advanced Mode (hit F2) and then Settings > IO Ports (arrow keys and enter):
Inside IO Ports go down to SATA Configuration:
Inside SATA Configuration, select RAID and enable NVMe RAID:
Then re-install Windows 🙃 I've even manually gone through and updated all the devices to the latest 9.3.1.19 driver stack, and haven't had any issues. RAIDXpert2 seems to still see all the drives just fine, and I haven't noticed any I/O issues.
- https://www.catalog.update.microsoft.com/ScopedViewInline.aspx?updateid=a905d038-2edc-434a-a53f-a47760921b2f
- https://www.catalog.update.microsoft.com/ScopedViewInline.aspx?updateid=bf0e1263-af47-4394-8bce-87b07db82984
- https://www.catalog.update.microsoft.com/ScopedViewInline.aspx?updateid=cce09a4f-e4f0-4cea-a4f7-c77d8ee477d3
The trick to installing the CAB files is extracting them, and then for the AMD-RAID Bottom Device I had to do Update Driver -> Browse my computer... -> Let me pick ... -> Have Disk (select folder where extracted CAB happened, most likely the "Downloads" folder.) -> Click on AMD-RAID Bottom Device -> Next -> Click "Yes" accepting the warning that this driver is not recommended.
Hopefully this helps someone fix their system or learn something new.