In some regions of the world a phone that is not considered "certified" by Google is only useful as a paperweight. For example, I wouldn't be able to interact with government services or use any banking with such a phone. (Notice the any and with — no, I can't switch to another bank except by emigrating somewhere, and banks are only available as mobile applications. No web.)

So unless you're willing (and can afford!) to buy and carry multiple phones, the new severely downgraded Android is about as open as iPhone, but with zero expectation of it respecting your privacy.

Or... you just register with Google and sign things using your own keys to authorize them before sideloading. Or setup an LLC or whatever and register that entity with Google or whatever.