Choice for single org or na

Could you explain your use case further? As a user will always belong to the default org - https://docs.kinde.com/manage-users/about/#users-and-organizations

I've talked once with Oli about that. It's just like for my use case I don't need nor want a user to be part of multiple org as it will happen when a already registered user will try to register again from a screen made for another org

Got it. Could you explain further your ideal sign-up flow? As there is a mix of org_code and adv orgs that might solve this for you.