No amount of dedication or care will provide you the level of privacy you believe to want.
You will waste time and energy, to ultimately come up with a greatly inferior user experience.
You might believe this is going to bring you peace of mind, but I predict it will only contribute to the paranoia.
I recommend you accept and embrace transparency. Privacy will only keep getting more and more expensive, while transparency is bringing much more value and opportunities than privacy ever could.
I will be happy to help you find a phone once you identify realistic needs (of which privacy isn't one).
Unless you're a spy, in which case carry on.