The key is stored in the BIOS (UEFI flash chip) - you can install 10 or 11 from the downloaded installers MS offers; as long as the Home or Pro is correct it'll activate just fine.
You can verify the key exists by running
hexdump -C /sys/firmware/acpi/tables/MSDM
Has anyone ever been as far even as decided want to do look more like?
(I'm ashamed to say that's from memory... and completely incorrect at that.)