Happy to see you SDH are still here! I've read a bunch of your older posts on these matters - lots of hard learnt findings!
Yeah, I'll probably end up wasting more time than 1 hour with the clip, but at least it's a challenge! I clipped another HP system successfully before, so have decent hopes.
I forgot to mention that one of the reasons to mod the BIOS was achieving direct NVME boot, but I guess nobody managed to flash that back either? Only that CLOVER approach with the USB key to bootstrap NVME?
I've daisy chained a few mods together into a single package hoping crisis recovery would bail me out if things go south - older microcodes/NVME/ReBAR, so tough to say if it's 1 change that bricked it, or some checksum issue. If I recover it, probably won't try again.
Apparently, Management Engine is a curse to many people given its opaque nature, so manufacturing mode can be leveraged for some of those objectives.