In fact IMO "highly integrated chips" such as SoCs are usually so complicated that no single individual really knows what's in them. And that's even when a chip is designed totally in house. However, most chips have lots of 3rd party Intellectual Property in them.

If my life depended on it (e.g. being a dissident in Iran or Syria) I wouldn't trust any cellphone.

If pressed, I would probably use a relatively old laptop and run OpenBSD. With no GUI, just a text login. And then I'd still be concerned that there are 10 exploits that TLAs could use against me, that they keep under tight wraps.

It's not paranoia if there really are people out to kill or imprison you. "The man" has so much power nowadays that I'm glad I'm living a sedentary life in a random suburb, and I'm not playing any sort of "You Bet Your Life" game.