I found a way to get NVMe booting on an X1 Gen3. Here are the steps;
I first installed Windows 10 on the NVMe SSD with it installed in the X1
You'll need to set the bios to UEFI boot mode with secure boot disabled
You'll need a USB thumb drive (Samsung fit works well)
Format with FAT32
create directory structure;
\efi\boot
download
https://github.com/tianocore/edk ... Shell/X64/Shell.efi to \efi\boot
rename \efi\boot\shell.efi to \efi\boot\bootx64.efi
download
https://tinyurl.com/y7ajr2vn and extract Nvm.efi to \efi
Create file with editor \efi\boot\startup.nsh
contents for startup.nsh;
@echo -off
load FS0:\efi\Nvm.efi
map -r
FS0:\EFI\Boot\bootx64.efi
Unmount USB and insert in X1 Gen3
If you didn't previously; in X1 Bios make sure Secure Boot is disabled and boot is set for UEFI
In boot order make USB HDD 1st or only option
Reboot X1 and press ESC on 2103 error, wait for EFI shell to load and execute script
Windows 10 should boot normally