I am using a macOS package (See wikipedia description) in an iOS app with a UIDocumentBrowserViewController. If the package is stored in iCloud, everything works as expected, but if the package is stored in Dropbox, it is shown as a package in the Dropbox App and in my app's document browser, but cannot be opened (it remains greyed out with the download indicator in the upper right corner of the file icon). How do I make this work for my users other than direct them not to use Dropbox?