Working demonstration of loading and saving data from/to device memory on Android in a Python/Kivy application. Tested on Android 6, 10, and 12 (Kivy 2.1.0).
The app allows to open any text file from anywhere in your device memory (or connected cloud services) and see its content in the text input field. You can also input any text yourself and save it as a new text file in the Documents folder on your device. In parallel, just for demonstration purposes, an .mp3 file is created and placed in the Music folder.
Read github.com/Android-for-Python/androidstorage4kivy for more technical details on how it works.