If you’re scratching your head with one of these laptops, the magic thing you need to know is that the BIOS (version 1.19 anyway) will only boot a file with the path and name of:
/EFI/Microsoft/Boot/bootmgfw.efiFor my Debian install, I copied the contents of /EFI/debian into /EFI/Microsoft/Boot and then renamed shimx64.efi to bootmgfw.efi
I wasted a day on this so that you don’t have to. You’re welcome!