The Apple TV app on Sony smart TVs unfortunately doesn’t support in-app financial transactions at this time. That means that any buying, renting, or subscribing has to be done on a different supported device (e.g. iPhone). Once the transaction is done, you may view that purchased content on any of your devices with the Apple TV app, when signed in with that same Apple ID account.
The website tv.apple.com is for Apple TV+ content only. Not buy or rent titles, not third party subscriptions.
Buy or rent titles can be purchased in the iTunes application on Windows computers.
Subscribing, or buying, or renting can be done in the Apple TV app on iPhone, iPad, iPod Touch, Mac, and several other supported devices. Unfortunately not in the app on Sony smart TVs at this time.
2. On Amazon Fire TV, Android TV, and Sony TV devices, you can't purchase content from the Apple TV app. You can buy, rent, or subscribe on another supported device and then watch in the Apple TV app on your Amazon Fire TV, Android TV, or Sony TV device. [2]