Hello Filippo Iacobellis,
Thank your for posting your query in the Microsoft Q&A Community.
Please be informed that Azure B2C tenant is designed to allow consumer users have access to your application using their preferred identity to get single sign-on access to your applications.
This tenant functions differently from the Entra ID tenant and most policies are either inherited from the Entra ID tenant where the B2C is created from or configured via Userflow or Custom policies.
Kindly click on this link to get more information about userflow and custom policies.
https://video2.skills-academy.com/en-us/azure/active-directory-b2c/user-flow-overview
You can take a look at some sample custom policies created for different scenerios in the Azure B2C tenant.
https://github.com/azure-ad-b2c/samples
Let me know if further clarification is required.
Babafemi