I'm quite new here, so please bear with me.

Which is the official channel for the patch announcements?

Patch Finder: https://download.suse.com/patch/finder/
Update Advisories: https://www.suse.com/support/update/

The Update Advisories seem to be more complete due to the additional information on Security Rating. This piece of information doesn't seem to be available in Patch Finder. Is there a way to retrieve the rating from Patch Finder? Is it possible to request to include the rating in the notifications?

For the advisories, is there a way to subscribe to it? I can't seem to find a way to do this. Any APIs that I can use? Am I missing something?