Not just illiterate. How many people here have the time or desire to inspect every app they use? It's a ridiculous proposition. We all have better things to do.

Obviously the onus isn't on every single user to single handedly verify themselves that the software is correct. Do you check your government's finances yourself? So why should they even publish it? By your logic, that is.

The answer is that if it's open then multiple people with differing interests, such as competitors, or even independent organisations such as non-profit auditors, can check the code.

That's like saying that freedom of speech should be banned because most people have nothing to say. User rights needs to be there for the people who need it. The iPhone is currently a black box where it's very hard to know what is happening in it, that's a big issue in terms of privacy and accountability of the platform, not to mention the anti-competitive behaviours.

Is there a practical solution that isn’t a black box? For the general population, not enthusiasts.

Yes, there's a whole market for Android devices which are both opened and very secure.

I'm not even sure how something like T2 could be done with an open platform

Let the user replace the manufacturer's keys with their own?

Imagine grandma accidentally putting her phone number in instead of an encryption key.