The code must be ported to API 30, due to Google requirement (https://developer.android.com/distribute/best-practices/develop/target-sdk). On API 30 is mandatory to switch to scoped storage.
As bonus, the user will be able to select the folder for exportation (this is the only way to gain write permission to the folder).
We have to rethink the way to load the EGM grid file (at the time the file is loaded from the shared "Temp" folder, that is not accessible anymore).
The app is thought to be used also on old devices: this is the reason why we would to maintain, if possible, the compatibility with the old Android 4 platform (minSdkVersion 14).