As soon as you start going down the rabbit hole of state sponsored supply chain alteration, you might as well just stop the conversation. There's literally NOTHING you can do to stop that specific attack vector.

History has shown, at least to date, Apple has been a good steward. They're as good a vendor to trust as anyone. Given a huge portion of their brand has been built on "we don't spy on you" - the second they do they lose all credibility, so they have a financial incentive to keep protecting your data.