Don't know about Chromebooks; I have some Chromeboxes, all unlocked, and all of them show the Coreboot splash screen before booting but no nags or warning signs

Don't know about Chromebooks; I have some Chromeboxes, all unlocked, and all of them show the Coreboot splash screen before booting but no nags or warning signs. My Pixel7, however, since installing GrapheneOS shows a very detailed screen on boot indicating the operating system has been swapped. not a problem for me, but surely It'd raise alerts if I wanted to sell the phone. So it's not like phone manufacturers lack ways of telling the user that something happened. To me it's just the old security by obscurity mentality paired with greed: a lighter and open OS on the phone translates in less user data being exfiltrated, longer device life and potentially fewer sales of newer phones.