On Sun, 8 Sep 2019 14:21:59 -0700 Samuel Sieb wrote:
BIOS boots using MBR,
invokes Grub, which then (optionally) invokes UEFI to boot Windows. Or is this not possible?
You can't because the EFI services would not be available.
Could you have a separate grub instance that is UEFI and chainload over to it?