We are talking about hardware here so ultimately you need to trust some manufacturer, software algorithms don't help.

With SEV-SNP and Intel TDX I think it's possible to build a hardware platform that doesn't require the user to trust the OEM although they still need to trust at least one large American tech company that controls the root of trust.

But I don't think this is ever gonna happen for consumer devices. AFAIK it's only sorta kinda happened for any real-world platforms at all (but maybe someone can correct me).

Ultimately if your threat model includes Google as a potential adversary, and you are not in control of nuclear weapons, you are gonna have to make some serious sacrifices to achieve security IMO. Smartphones are out. (Actually, I guess if you trust China you have a way forward).