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

[pynicolas]

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"