Apple TV app Channels are a special case, as these are essentially copies of their catalog, hosted by Apple, and with special terms and conditions, perks and limitations. Subscribe to Apple TV channels in the Apple TV app - Apple Support
Apple TV Channels FAQ: Services, pricing, availability, and everything else you need to know - Macworld
Select third party apps can choose to “support” the Apple TV app, allowing cross-app linking of their content (on iPhone, iPad, and Apple TV box), for Search, Watch Now, and Up Next, by sharing show information. The source app is still needed. Availability of supported apps in the Apple TV app - Apple Support
The Apple TV app on Mac doesn’t have other streaming apps to link to. Other streaming services have to be accessed on Mac in the browser. This feature isn’t available on Macs (or on third party devices).