Is there a way (RSS, mailing list, some site...?) to be notified when Debian updates a package? I mean any package, not a particular one or the ones I have installed on my machine.
debian-devel-changes mailing list receives a copy of the upload descriptions for all packages uploaded to Debian unstable and experimental,
debian-changes to stable,
debian-backports-changes to backports.
debian-security-announce receives all security announcements (when they’re ready for publication).
You can subscribe to those to be notified of all package uploads (which means a lot of email).