Hi @simon_qollabi,
organization_name is the correct URL placeholder. If you represent tenants in your application as the same string as the organization name, you can send that as a redirect URI and it will validate.
As an example, if you had an organization with organization name acme, and the allowed callback URL had https://{organization_name}.myapp.com/callback you could send a user with the redirect_uri: https://acme.myapp.com/callback and it would work.
Example authorize URL that the user would be redirected to:
https://[tenant-name].[region].auth0.com/authorize?client_id=[client-id]&scope=openid%20profile%20email&response_type=code&redirect_uri=https%3A%2F%2Facme.myapp.com%2Fcallback&organization=org_O6uxTfoyxaOylFIR&nonce=[nonce]&state=[state]
Re: B2 this is on our roadmap, though I suspect you could do this with a rule currently.
Re: B3 - updating that, thanks for catching!
Re: B4 - I hear you. We are actively considering this but I can’t confirm if we’ll allow this or not in the future currently.
Re: B5 - can you share the specific error you are getting? Does the auth0 database connection perhaps have signups disabled?