This is on 4.2 without running without the stubdom pach so no prefix should be required, but I did have it there nonetheless.
Applying the stubdom patch on a clean 4.2 install does get it to boot with 32GB of memory, but I’m getting the same blue screen shortly after boot as here HVM no bootable device after gpu passthrough - #12 by Cameron and no PCI devices except the NVMe are functional.
Removing the prefix and setting the memory to 2GB allows it to boot part way but it throws the same bluescreen before it boots fully (nvlddmkm.sys). Removing the GPU allows this one to boot fully but again none of the PCI devices except for the NVMe drive appear to work.
The PCI devices all appear to not function as well, no network adapter, no USB, no GPU apart from the 4 sensors it briefly displays before BSODing.
I have tried with and without Above 4G Decoding (I had this on previously, doesn’t seem to have any affect) and Resizable BAR (this prevents Qubes from displaying video at any point past GRUB for me)
Going to install 4.1 and see if that still works properly.
EDIT: Fresh 4.1 install with just the stubdom patch applied works perfectly so it’s definitely an issue with 4.2.