From my perspective, distro-provided add-ons should be shown together with those provided via KNS, but at the top of the list (ideally with some kind of separator like a section header)

Rationale:

1. Although distro-provided add-ons should be preferred over KNS-provided ones due to better quality assurance, they are not fundamentally different, as both extend the application's functionality
2. Distro Add-Ons should also be shown when manually browsing through the "App Extensions" section