Not much to say... a friend and I corebooted our beloved Thinkpads x220, removing also the Intel Management Engine. We used a Raspberry with a Pomona clip to read/write the bios.

The only drawback is that we couldn't set the initial splash screen, I'm reading that it has to be a jpg with a voodoo color space and a non-progressive setting. This is the handmade bootsplash, ready for the next time: