[stonogo]

In order for libreboot or coreboot to support a system, that system must be almost entirely reverse engineered. As Intel shoved more and more functionality into ME, they also ramped up how aggressively they protected those parts of the system. There is significant crypto involved at this point, and Intel considers almost every component a trade secret to be fiercely protected. It's almost impossible to get access to this information, even under NDA, even as a hardware manufacturer (i.e. system OEMs).

It's not for lack of trying; the lack of adoption is because Intel is actively hostile to efforts like these and they hold all the cards.