Hi @agujonas13
Welcome to the Auth0 Community!
I’m sorry for the late response to your question.
The main thing that you would be interested is post-login action that contains event.stats.login_count property → Actions Triggers: post-login - Event Object.
Optionally if that’s an option for you you can use a Pre or Post User Registration Action, but they will trigger only for the Database or Poasswordless Connection types.
In terms of redirecting them to the onboarding route you can utilize the the post login action to conditionally redirect user to the external site Login Flow
I hope it will help you
Thanks
Dawid