Android 11+ enforces scoped storage, which restricts access to the filesystem in many cases.[1] Syncthing requests the "All files access" permission[2] to get around this, but the /sdcard/Android/data directory (private app data) is still off limits.[3]

[1] https://source.android.com/devices/storage/scoped

[2] https://developer.android.com/training/data-storage/manage-a...

[3] https://github.com/syncthing/syncthing-android/issues/1638