It is unfortunately possible to have driver perfectly installed and STILL get "inaccessible boot Device." The reason is a bit shocking (I find): a Win 10 installation "remembers" the drivers that were required when it was first installed, and by default WILL NOT load other storage drivers at boot time. This is done, it seems, to "piracy" -- it makes it difficult to run the "same" installation on different hardware. There is some great documentation on this "feature" in this post from the gentoo forums. The essence is as follows:
The Drivers that are targeted for forbidden-to-load-at-boot can be determined as follows:
Within the registry key Computer\HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services there is one subkey for every driver known to the installation. The name of this subkey is just the name of the driver. Within each driver subkey, there will be a subkey "STARTOVERRIDE" if that driver is to be prevented from loading at boot. In particular, within the STARTOVERRIDE subkey there is a parameter whose name is "0" . IF the value of this parameter is "3", it will not be loaded at boot time. Setting this value to 0 instead will 'override' behavior.
I myself just go to Computer\HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services and search for "STARTOVERRIDE". Each time i find it, if there is name under it called "0" with value "3", I change to "0". This seem to be overkill, you only need to change the drive that needs to load. In my case there are several of them, and I never remember which, so I just do an "F3-search" within that 'services' section.
And one final tip which isn't needed for current, signed, virtio storage, but might be to someone else reading this if they want to use a more experimental driver that is not (yet) signed: I found that EVEN after doing the above trick, I ALSO needed to boot into the advanced options screen and choose F7 ("disable driver signature verification"). Annoyingly, it wasn't enough to set the bcd flag to disable driver verification, because the driver needs to load before the machine reads the BCD and finds out that it doesn't need to verify the signature.
All in all, not Microsoft's most shining hour. You really have to hate your users if you'd rather give legit users a made-up artificial Blue-Screen than allow people to (say) replace a SATA disk with an NVMe disk and have it "just work."