This modern bios volumes space issue has been an issue for a long time. You will not be able to replace microcodes with UBU. You’ll have to get down and dirty with a hex editor. That non-empty Padding file under File GUID: B52282EE-9B66-44B9-B1CF-7E5040F787C1 needs to be maintained.
Even though UBU (MMT 5.2.0.24 or UEFIReplace v0.25.0) can’t properly deal with the no free volume space, there is plenty of FF room in the Padding after the last microcode. FF’s were removed there to maintain proper size after accommodating the new, larger microcodes.
I’m away from this computer until Sept 10, so I can’t test it for a while, but I’m pretty confident that I got it right.
[EDIT - FIT Table broken BIOS removed - see posts below]
The attached is the full bios after hex work that only deals with updating microcodes. As you’ll see in the text file, I did run the bios through UBU to update other stuff. But given the overall UBU volumes space limitation issue, a UBU “other items” modified bios may still present problems. The other mods did present size changes. I may or may not bother with flashing beyond updated microcodes. It’s not easy physically flashing with the 16 pin clip if updated other items break the bios.
I’ll follow up. If this works, it will probably be possible to FPT flash the ucode with fptw64 -a 0x1D50000 -l 0xF0000 -f ucode.bin once you’re up and running with the original bios fix and updated 2.33 from Dell. Of course, that won’t be necessary if my attached bios is good, and you’re physically flashing a bricked box.