it’s only open in words, the android phone you purchase from oems contains plenty of proprietary stuff, not only from the oem itself but from google and and even the chipmakers like Qualcomm as well and in some cases like play integrity, an open alternative doesn’t exist on top of that, oems don’t just receive the aosp from google for their devices but something called partner sources as well and i don’t know much about them except that they aren’t publicly available
edit;and yes as you might have expected a lot of hardware in your android phone is pretty unusuable without proprietary stuff though i think i am sidetracking from the main topic at discussion now…