I want to create apk files for the games I’ve purchased on Google Play. If I use the Google Files apps, it won’t compress the whole game into apk (for example, APK file size for ‘Bendy and the Ink Machine’ is only ~2mB.) For now, only local backup seems to be the functional method.
There’s a few apps out there that can copy the apk, however it won’t copy user data, so unless the app you’re backing up has a way to export/import (or if you have root access) you will only be able to copy the app itself. If that is what you need, Link2SD has been quite reliable for me for about a decade for managing and backing up apps so i recommend it.
Another thing worth mentioning if you are trying to do an offline install, some apps have a license verification check that won’t let you run the app unless the account on the device has a valid license for it.