OK, thank you.
Nothing wrong with the bios update for the bios region, code parts are identical to stock bios. So it might be something in NVRAM (unlikely) or a corrupt ME (but it got updated to the version in the Dell update- so unlikely, too) or something not firmware related (probably).
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Extract the latest Dell update
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Exchange as is the bios region of your dump with the bios region in the update ‘1 O3010A22 – 1 System BIOS vA.22.bin’ (UEFITool 028 or 025)
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Transfer the DVAR padding 0x240000 - 0x250000 into the stock bios region (HxD)
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Clean the ME of the created firmware image according to:
https://winraid.level1techs.com/t/guide-clean-dumped-intel-engine-cs-me-cs-txe-regions-with-data-initialization -
Flash the image back, double check if the writing was successfull!
You tried a lot of found images already, those machines are old, chances are good that there are working image(s) floating around, so I don’t think it’s firmware related…