You need to have a wifi only android phone, rooted, no google apps, and uninstall anything that talks to the internet. That includes analyzing network traffic,

You need to have a wifi only android phone, rooted, no google apps, and uninstall anything that talks to the internet. That includes analyzing network traffic, open ports, and so on. I did this with a Kali Nethunter distro back in the day for "reasons", privacy not being one of them. This makes the phone very hard to use for regular things.