I know Ron Minnich. He is one of the founders of the coreboot project. He's been at this (replacing proprietary firmware with a free software alternative) for a very long time and he knows what he is talking about.
But... replacing Minix with Linux wouldn't be replacing proprietary code with a free alternative. It would be replacing free software with a less free alternative.
Your use of 'free' here is correct from the perspective of a developer working for intel, but as a user with a cpu running modified and previously opensource, but now closedsource, software it isn't applicable to me. GPL would have protected more of my freedom, provided they didn't just violate the GPL.
https://schd.ws/hosted_files/osseu17/84/Replace%20UEFI%20wit...
I know Ron Minnich. He is one of the founders of the coreboot project. He's been at this (replacing proprietary firmware with a free software alternative) for a very long time and he knows what he is talking about.