AdminUI uses a custom ASP.NET Core Identity schema. This schema extends from the ASP.NET Core Identity Entity Framework defaults, meaning any registration, password reset or login functionality you might already have, will continue to work with the AdminUI user store.
However, any existing users will need to be exported to use the AdminUI schema. For more details, see the Migrating to the IdentityExpress Identity Schema section of this article.
This schema is available in the nuget package
IdentityExpress.Identity. Check out the Admin UI IdentityServer integration example for a working IdentityServer installation using this nuget package and schema.