How can I read out complete coreboot and valid it after boot

I want to read out coreboot code after starting it and valid it with sha256 to check the integrety (with qubes os)

Perhaps you need Librem Key:

I can use flashrom -r

But I have a question. Is the coreboot img after first running changing? (when you flash it) because with flashrom -v coreboot.img is showing no verification after restart the librem