We have integrated google and apple login in flutter.
The webview opens in the Flutter app and there is a button that opens the google or apple login button from the webview.
We then call the SDK to get the user email, ID and other info from the SDK.
After that we use the post API https://xxx.backendless.app/api/users/oauth/googleplus/login and get the JSON response but when the user is redirected to the next page in the app they are not logged in.
There is also a custom domain on this instance in Backendless, if this makes any difference?