1. Acquire a device supported by LineageOS [1]

2. Unlock the bootloader

3. Install LineageOS with GApps (ability to run Google Apps and use the Play Store)

4. Enable root (it's an option in Developer Settings)

5. Disable/remove all other apps besides the ones you'd like to keep.

You need to be comfortable with commandline in order to use tools like adb (Android Debug Bridge) and fastboot. There are really good step-by-step guides on places like xda-developers though. Good luck!

[1] https://wiki.lineageos.org/devices/

Get a feature phone[0]. Not sure they have Google Maps on them though as I think that's an iOS/Android only thing.

[0] https://www.nokia.com/phones/en_int/feature-phones

It's not smartphone fault that you are addict.