Channels does not actually record from YTTV. It uses your YTTV credentials and TVE to log in into to the network website and capture the live stream if available. You would need a Homerun/antenna or paid Locast to receive your local stations.
If you have Apple TV you would use it to access the Channel's app, Amazon, Netflix, Disney. You would not use one app to view everything, but you would use one device to view all the apps. If you wanted one app to view all your content on one screen, check out Playon. It records content from various sources Att TV, Disney+, HBO. But it does not show live tv and only records the shows when they are available On Demand not live(as Channel DVR does).