AirPlay not working on Apple TV Model A2737 (Apple TV 4k)

After updating to iOS 26 and tvOS 26, Airplay from iPhone 16 Pro to Apple TV Model A2737 no longer works when trying to AirPlay nearly all (over 90% of) YouTube videos using the YouTube iPhone app. The TV screen is black with a red circle with the red line through it at the bottom of the screen. I tried restarting both devices, resetting the Apple TV, resetting my network settings, and adjusting resolutions. Red circle prevails.

Conversely, Airplay from the iPhone to both of my Apple TV Model A1625 still works for all YouTube videos. No issues.

Airplay from YouTube.com on macOS 26 to Apple TV Model A2737 also still works.

Yesterday, I saw a post on Reddit (that I can't find again now) where other people were having the same issue trying to AirPlay YouTube app videos from iOS 26 to the Apple TV 4k (A2737).