Go here for the outstanding issue of using UBU to modify and flash the Winbond W25Q256JV 32MB bios chip on these Dells.
SoniX
The bios is new, the sizes are 32, and the problems are old - there is no free space in the volumes.
Potential solution in this thread. Maybe, maybe not.
Edit: BTW, there’s no issue with flashing with the Intel ME Flash Programming Tool (FPT). It’s a fundamental problem with volumes space. If you UBU modify the bios and flash with a programmer, you’ll get the same result.