iTunes Extra and Apple TV app on Windows

Frankly, this is an unacceptable user experience from a multi billion dollar corporation. Every part of the experience prompts you to move permanently to AppleTV and Apple Music apps with no indication that you're taking part in a beta. Instead you just lose features like itunes extras, despite their presence still being marked on the store page as playing on the AppleTV app, the movie I purchased then also only seems to play up to 720p, and on top of that closing the player window without closing the whole app just leaves the screen permanently black until I either manage to blindly close AppleTV or restart the computer. That should not be the experience that users are being prompted to switch to.

I'd say downgrading is an option, but then you need to reinstall everytime if you want to view AppleTV+ content and old iTunes is playing the movie with heavily washed out black levels. So a lose, lose.

I think just refunding my paid content is the only way forward at the moment.

Seems so. The new Apple TV Users Guide for Windows (1.4) also curiously does not portray, describe, or otherwise mention iTunes Extras, or their associated player controls, banners, etc., either. I could find only one, indirect reference to viewing Extras previews in the Store section of this guide. In practice using the new app, my own Store purchase record indicates (displays) that I have purchased many movies with iTunes Extras Included. Not one of those movies shows, accesses, or plays their Extras. I've provided separate feedback to Microsoft Store Support (app) and Apple Support (app / guide), too. I own both PC and Apple platforms; my iTunes Extras play on all my Apple OS-variant devices.

The Apple TV app on Windows is still considered Preview/​pre-release software, which may not be feature complete yet. Does the app have a built-in feedback mechanism or link?

Else give feedback through: Feedback - Apple TV App - Apple.

(Glitch....Ignore.)