Brightcove portal domain indexed instead of custom domain

Hello,

we are using a Brightcove Video Cloud portal with a custom domain.
However, Google is also indexing the native Brightcove portal domain as well.

This results in duplicate URLs for the same video pages, for example:

If we prevent the Brightcove native domain from being indexed, what happens to existing URLs that may already appear in search results or external links?

Does Brightcove support redirects from the native portal domain to the configured custom domain, or is there another best practice to ensure only the custom domain is indexed?

Thank you for any guidance.

-Frank