I feel that this is a rather poor question, and comes off as a little immature and naive. If I had to give it a bash however, I'd reckon that a phone would be c

I feel that this is a rather poor question, and comes off as a little immature and naive. If I had to give it a bash however, I'd reckon that a phone would be completely unecessary. Reducing your technological devices down to solely your computer limits your surface. Then I suppose a librebooted QubesOS (although this is hard to do admittedly), using as much open sourced hardware as possible. All internet would be routed through Tor, and I suppose an even better idea would just to boot the entire thing on Tails or even Kali when needed for convenience off a clean USB. Encrypted hard drive along with avoiding proprietary drivers too. For software, messaging would be done via Matrix or Signal, no software other than what's strictly necessary for the task either. There's so, so much more that goes into staying anonymous as well as secure other than just your tech stack, as other commenters have pointed out.