Create an “Onboarding Complete: true / false” option in your User database. When a user has completed the onboarding, set an action to mark “onboarding complete” as True.
Put a blank “user direct” screen before the onboarding screen (set as the home screen) with automated actions when a user visits the screen. If onboarding completed is marked as true, direct them to the login screen. If false, direct them to the onboarding.
I have my “home screen” set several screens prior to the IAPHub with various redirects, IAPHub will still work correctly.