I have a burner phone with pay as you go sim and a series of grapheneos phones with no sim that tether to the burner phone and use tor. Each phone is for a different app, one for email, one for browsing, one for messaging. Each time I read an email or a message, or browse to a new webpage I destroy the phone after using a custom built thermite incineration case. It's expensive but they haven't caught me yet.