You will be able to boot OS from NVME (I'm using 970EVO) using the full UEFI 2015 build.
Steps required:
1. Get the UEFI 2015 build
2. Add the NVME Drivers to it (I made a folder named EFI\Drivers) and renamed the file to a shorter name - Nvm.efi
3. Customize your startup.nsh script to load the drivers and boot the OS (see below)
4. Put the cooked EFI on a bootable stick, which will always stay in the machine (I use a 512Mb one, really old :P )
5. Modify BIOS so it boots from USB
How I customize startup.nsh with the script:
echo step1
connect -r
set -v efishellmode 1.1.2
map -u
echo step 2
load fs0:\EFI\Drivers\Nvm.efi
echo step2
map -u
echo step3
fs1:\EFI\boot\bootx64.efi
where fs0 = bootable stick
fs1 = Samsung 970 Evo ;)
Or, if you're in a rush:
Here's the final EFI build (you might need to change the fs** numbers, based on what you have going on in your machine)
https://drive.google.com/drive/folders/1muN3k_eXJ2PcZfDWtWEmpG0ga-nUVNxv?usp=sharing
My numbers (z620 + 970EVO)
Regards,
LevelsAndMaps