Hi! I am new here and I have an old Dell T5600 (A19 firmware revision) that I am attempting to mod the BIOS/UEFI for NVMe support. Initially I was using Clover, which worked, but did have some drawbacks. So, I wanted to attempt to modify the BIOS/UEFI to add NVMe support instead.

After a few fumbles (initially extracted and modified a stock firmware update from Dell exe), I have dumped the current BIOS from the board using fptw64. I have then used the UEFItool to insert the NvmExpressDxe_4.ffs, and saved back out correctly sized .bin. Before flashing the modified file, I tried to flash back the original dump to check for errors. This however results in the error, “Error 280: Failed to disable write protection for the BIOS space!” Now, I have read about using AFU to bypass, but also read that I shouldn’t use AFU anymore, so I am at a bit of a dilemma.

I found a guide with some ideas, but it seemed to be related to Asus motherboards. So, other than using a hardware EEPROM Flash programmer, what software options do I have available?

PS: Thank you for all of the great information here.
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Actually, I may have found a solution. This board is equipped with a service mode jumper. Sorry, so much to read in this forum. I am sorry for asking for something that already has answers. Sometimes sifting takes a bit of time. I will update with the result. Thanks!
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Alright, so I attempted to flash my modded BIOS, and my system locked up. Granted, I tried to flash from Windows, and I was already running on the NVMe drive via Clover. So, I used Rufus and made a bootable flash drive and flashed from there. It seems to have worked. I didn't do a fresh install of Windows, but I did have to go into the BIOS setup, change to UEFI, and point to the correct boot file. I know it is odd for me to say thank you when I am the only one participating in this thread, but I just want to say "Thank You" in general for all of the information on the forums. The info on this site helped me a ton.

@LordDagon - Please edit your posts when you need to add more info, questions, thoughts etc and no one has replied yet, thank you

This guide will help you get around error 280 sometimes, this depends on how that lock is being set - [GUIDE] Grub Fix Intel FPT Error 280 or 368 - BIOS Lock Asus/Other Mod BIOS Flash
Alt boot to grub when no boot to EFI on exit page - [Help needed] Hidden Advanced menu Bios HP Z1 J52_0274.BIN (2)

Zip your FPT BIOS region dump for me if you cannot find the setting in IFR. Seems you got around this via service jumper, so you could flash via FPT without disabling the lock causing error 280, good job noticing the jumper I always forget to tell user to look
If you want to try and disable that so you don't have to use jumper, send me your BIOS region dump and I'll tell you how to disable via grub/setup_var