Coreboot is a great idea, and I actually considered using it, but the project looks woefully under-powered for the role it hopes to play: the list of supported devices is very sparse and consists of really old models, mostly; even the supported systems have issues and/or untested functionality. http://www.coreboot.org/Supported_Motherboards
I haven't looked into the relationship Chromebooks have with Coreboot: supposedly, Chromebooks use Coreboot, but how is it possible that they restrict the usage of OS to a signed one: do Chromebooks use modified Coreboot? And why is some models' status listed as "Unknown" in Supported Motherboards list?
So, I would love to use Coreboot and would actually consider going into some reasonable trouble to make it work on my hardware (including actually picking hardware that it supports), but I really don't see how it would be usable even for an enthusiast, and I don't see the situation changing anytime soon.
They restrict use to a signed OS through their payload. coreboot only does hardware initialization, then passes control to other software in flash that handles loading the OS and policy surrounding it.
As for the "Supported Motherboards" list, it's automatically generated from reports that are sent in through a tool. Google doesn't do that (yet?), so they're not listed as supported.
Still better than our old, manually maintained list, that got stale fast (with false positives, which are much more annoying from a support standpoint than false negatives)
All x86 Chromebooks (except for the CR48 prototype) use coreboot.
For ARM Chromebooks the situation is more complicated - coreboot's ARM support was developed by the Chromebook firmware developers but it seems they missed a deadline or two (no surprise with an architecture bringup), so some of those devices ship with u-boot while coreboot does have support for them.
I understand it means that to the best of Coreboot developers' knowledge (and who knows better than them, right?) noone ever tried to run open-source builds of Coreboot on these models. Consequently, it is overwhelmingly likely that Coreboot (the open-source version that we have access to, not the one in the Googleplex) won't work. Am I mistaken?
I considered using C720 Chromebook with open-source Coreboot, but, alas, it says "Unknown" for it, too.
No, it means that noone bothered to send in reports.
http://johnlewis.ie/ provides non-Google coreboot images for many Chromebooks. They claim having tested each of their binaries and from looking at the support forums, they have a fair share of users.
I haven't looked into the relationship Chromebooks have with Coreboot: supposedly, Chromebooks use Coreboot, but how is it possible that they restrict the usage of OS to a signed one: do Chromebooks use modified Coreboot? And why is some models' status listed as "Unknown" in Supported Motherboards list?
So, I would love to use Coreboot and would actually consider going into some reasonable trouble to make it work on my hardware (including actually picking hardware that it supports), but I really don't see how it would be usable even for an enthusiast, and I don't see the situation changing anytime soon.