Your best bet is to get a phone compatible with custom roms. Like lineageos, calyxos, grapheneos, etc. The Google Pixels tends to be the few modern phones that still support a custom rom, without being a phone from 5 years ago. Unlockable bootloader, and a pretty repairable phone if the battery dies or if the screen breaks. Make sure it's an unlocked phone, otherwise the sim card company won't allow you to use custom roms.