using Berlin 10.1.2 i made an iOS app. With your FMX Cloud Pack it has Dropbox storage access.
After 50 linked Dropbox users i aplied for production review - that got denied with the following response:
Your app currently processes the OAuth app authorization flow inside a
web view, instead of the system browser. In order to support the Google Sign In
flow when signing in to authorize the Dropbox app, your app will need to be
updated to use the system browser, in order to comply with Google's policy: https://developers.googleblog.com/2016/08/modernizing-oauth-interactions-in-native-apps.html
Further, when i try to follow your recomandation to set the property "ExternalBrowser" Delphi doesn't find it. If i write it by hand and compile Delphi displays the error message "E2003: Unknoen identifier 'ExternalBrowser'.
Please note that the ExternalBrowser property is currently only available for the Windows platform. If you are developing an iOS app the ExternalBrowser will currently no be available.
The availability of the ExternalBrowser property will be extended to other platforms (including iOS) in a future version of the TMS FMX Cloud Pack.