@prettygood >I'm fucking going full stone age and getting a boomer flip phone.
The thing is that you can't - most places have shut down the GSM network and the remaining will eventually shut them down too, as UTMS and LTE have an exponentially larger spying/frequency band utilization ratio (although there will remain a few remote locations with only a GSM network).

You want a VoIP phone, that just connects to the internet (preferring via your freedom-respecting LAN or Wi-Fi, but you can also make such work remotely with a external mobile card and a cheap data-only plan).