Awesome post, but a very minor nitpick:

> Chromebooks use both, coreboot on x86, and u-boot for the rest.

This isn't entirely true. Coreboot is used on a number of ARM Chromebooks, including rk3288 and rk3399 based devices. It seems like u-boot is used less and less in the space. Libreboot has builds for a few devices that kill the annoying "untrusted os" message, and even allow you to set your own trust root.