M2 Boot on Legacy Bios Motherboard

I have been attempting to boot from an M2 drive mounted in a PCIe adapter on an ancient Gigabyte GA-H55M-UD2H motherboard. The PCIe is version 2. The M2 drive can be seen, written to & read but won’t boot

Some say that booting is only possible with UEFI whilst others say it is possible using a legacy bios & an intermediary boot loader eg Clover or Duet.

Any insights?

Clover Bootloader
– https://www.win-raid.com/t2375f50-Guide-NVMe-boot-w-o-BIOS-modding-Clover-EFI-bootloader-method.html

DUET – Developer’s UEFI Environment
Duet + rEFInd (direct download)
– https://drive.google.com/uc?export=download&id=1ogEdBzKrLRkz0SRwLphpFemRLWmgayA-