HDTVTests review of the C9 found that in it's service menu was a history of HDMI devices connected, this is likely why it recognizes the AppleTV.
If you still cannot edit the label as per Brandon's instructions it could be LG's engineers didn't put enough thought into the system and that people may still want to change the labels even if the TV auto detects the devices correctly.
Please help to start develop Unifi PlayTV for LG TV WebOS.
Currently the built-in apps available for Samsung Smart TV and other standard os ie ios, android.
Appreciate LG developer can work on development of Local content apps. (Malaysia).
The two methods I know of are to cast it from a mobile device with Chromecast, and subscribe to it through Amazon Prime Video, which has an app on the TV. I don't know if Roku or Fire Stick has the app.