Hi
Power Apps Portals is fully integrated with CDS, and that's your database.
whatever other platform you want to integrate with the Portals, you should look as integrating with CDS/D365 as that's the source of the Portal data.
As an example, let's say you have a news & announcements page where you are rendering Content Snippets of that type (you can create a custom field or have a naming convention for example) and then your integration can create new Content Snippets that would be rendered in that page.
Is that what you need?
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