Is Apple TV compatible with

Comcast Xfinity is not a supported TV provider for Single Sign-on.

The Xfinity Stream app is not available on Apple TV.

Comcast disabled AirPlay in its Xfinity Stream app, so you can’t even stream from phone to TV.

They really want you to use their own set-top box instead.

IF you convert over to Direct TV, Direct TV does have an app that runs on Apple TV. This would likely provide all the content you have on Comcast.