Coreboot can somehow disable ME if you tell it to by some configuration option, it does that in a first few opcodes after enabling RAM.
Do you have any reference on that? All I can find on that is that libreboot can turn off versions of ME prior to version 6.0, but that versions after that will turn the computer off after 30 minutes.
I am using Libreboot on a Thinkpad X200.
As I understand it, the X200 comes with ME out of the box, but it’s possible to flash your own replacement firmware by grounding GPIO pin 33 which disables the flashing protections.