Export folder: selecting "Downloads" leads to 'Folder access lost" on Android 8

Reproducer on Android 8.0 and 8.1:
- Go the Settings screen
- Tap on the "Export folder" field
- Open the left side bar by tapping the ≡ icon at the top left
- Select "Downloads"
- Tap "Select"
- The settings screen then displays "Folder access lost"

