I don’t know how all this is working, all I did was download Elgato Game Capture for Mac & it saw all of my Apple TVs hooked up to the (same) wifi network as a source. Even on wifi, the latency seemed very low. All I had to do was enter a 4 digit code the Apple TV displayed in the Elgato Capture program and it started pulling in exactly what was on my screen. I don’t own any of their hardware, so nothing was plugged in at the time on my MacBook Pro. The TV showed a red border around the edge. There is also an app for iOS called Screen Link (I did see about 1 second latency going from my phone to my Mac using this app though, but both were on wifi). Saw a comment from one of the Elgato employees on Reddit, he stated they are using Apple’s ReplayKit API.
This would be so much more flexible and requires less hardware than the USB QuickTime capture or using a HDMI capture device. Since the Apple Lighting cable is required for USB capture, at only 2m it’s not practical in a lot of situations. Eliminating the need for HDMI capture lowers the entry cost for new ML users. Please consider this request and please let me know if you need me to put together a demo of this feature with the Elgato software. Thank you.