Adding this callback url in the settings, doesn't work with Firebase (doesn't show any user that signed up): [twitterkit-Consumer_ID://]
Adding this callback url in the settings shows error "forbidden (403)": https://the-app-name.firebaseapp.com/__/auth/handler
Everything in the info.plist was put correctly: consumer id, ....
Everything in App Delegate was put correctly: Twitter.sharedInstance.start..., Twitter.sharedInstance.application...
Help much appreciated