a) the in-use M.2/PCIe connected SSD is a Samsung one and uses the SATA AHCI protocol
Yes, my Apple SSD is a Samsung product with AHCI SSD Controller. here and here
b) the module named SAMSUNG_M2_DXE.ffs has been properly inserted and
Done. I’ve tried 2 versions of the SAMSUNG_M2_DXE.ffs(6,796Bytes and 6,741Bytes).
c) the modded BIOS has been successfully flashed
Done, with fptw64.exe.
Now I finished all steps of “Step 4” what you suggesed in >this<, but SSD still cannot de detected by the BIOS, I mean there is no device in legacy mode, and no EFI item in UEFI mode.