In years past I built my own computers from scratch with hardware components I trusted, and open-source software. These days I can't build my own hardware. I still use as much open-source software as possible. Past that, I just have to accept the residual level of risk.
Good post.
They key is to avoid overconfidence that any of us has privacy.
My baseline presumption is that if .gov has any issue with you then you have zero privacy.