Currently the Proton Drive Android app lets you sync local folders, but with a limitation: if you have a big folder containing multiple subfolders (like that you get out from a Google Photos takeout), the Android app shows all the subfolders individually, instead of letting you choose any of the parent folders. Selecting these subfolders can be tiresome if you have photos spanning 15 years. It would be really nice to have more flexibility in the choice of the folders to sync.