first of all I am new to Android development, so please excuse if the following suggestion is dumb.
I noticed that this app can’t be backed-up via “adb backup” although android:allowBackup is set to “true” in the AndroidManifest.xml. The resulting file simply contains nothing reasonable.
I have the following idea for what might cause the issue, maybe you can tell me if that makes sense:
In the AndroidManifest.xml (see https://gitlab.com/bitfireAT/davx5-ose/blob/master-ose/app/src/main/AndroidManifest.xml#L42), there is the line
This page https://developer.android.com/guide/topics/manifest/application-element however, says that “android:fullBackupContent” needs to be a string instead of a boolean:
This attribute points to an XML file that contains full backup rules for Auto Backup. These rules determine what files get backed up. For more information, see XML Config Syntax for Auto Backup.
This attribute is optional. If it is not specified, by default, Auto Backup includes most of your app’s files. For more information, see Files that are backed up. "
I thought this might be the cause for the issue. Does anyone know the reason for the value set to “false” in that file?