Why FBReader requests access to all files on Android?
Starting from Android 11, Google changed the file access policy. The app has a choice: only have access to its files stored in a hidden folder or request access to all user files. There is no granularity.
The first way does not work for an app that reads books from user folders. That would be nice to request access to files in the Books folder only. Unfortunately, there is no such choice on Android 11+.
An application needs two permissions to access all files. The first is from Google; it allows requesting users for such access. And the second is from you. Google has granted permission to the most popular book readers, including FBReader. It is your turn now. You can believe that FBReader does not steal or damage your data or can choose another reader you trust.