Can the built-in "No account? Create one" link redirect to a custom sign-up page?

I'm using Microsoft Entra External ID with a built-in sign-in/sign-up user flow.

On the Microsoft-hosted sign-in page, the "No account? Create one" link always redirects users to the default Entra sign-up page.

I already have a custom registration page and would like this built-in link to redirect to my custom URL instead.

Is there any supported way to customize the destination of this link in a built-in user flow? If not, could someone confirm whether this behavior is fixed by design?

Thanks!