The point (that is, the thing that matters, which admittedly you would have to actually read the thread for understanding) is that libreboot isn't available on enough platforms to be a free alternative to proprietary boot methods for most people. And that's even including all the chromebooks in the world. But Someone Is Wrong On The Internet, so I guess you can claim to have fixed that.
That said: most if not all of them require some proprietary bits to initialize ram timings and to run the security coprocessors (Amd PSP, Intel ME).
Older intel based systems (like the Lenovo x200) have coreboot support that can work without the ME firmware (but still requiring the EC firmware).
A list of many of the google devices with coreboot support (note: they're all codenames, not marketing names): https://doc.coreboot.org/security/vboot/list_vboot.html#goog...