When I use the UIDocumentPickerViewController with kUTTypeFolder I am only able to pick from the providers built-in to iOS/iPad OS, such as On My iPad, iCloud Drive, network shares and USB drives. As of beta 4, 3rd party providers are shown, but disabled (not selectable or browsable).
I have not been able to find any information on whether or not 3rd party providers will be supported by the release of iPad OS 13. I am hoping this will be possible in a future build (or at least something 3rd party providers can enable) since this is a big driving factor for enabling us to ditch a *lot* of custom cloud storage code.
Any info (or if anyone knows either way) would be much appreciated!
I have been instructed by DTS to file a bug report for this. For anyone else affected by this issue -- PLEASE file your own bug report so this can be properly escalated (e.g. looked at sooner than with only one report): https://feedbackassistant.apple.com