It is also very easy to set up iOS Shortcuts that wake the AppleTV (which also turns on the TV, if necessary,) open the Channels app, and tune to whatever channel you wish… via customizable voice commands to Siri. I do this often to jump between favorite live channels.
More information about that is here: Channels Support - Siri Shortcuts
For example, this API command embedded into the shortcut, tunes to ABC (channel 7.1) on my AppleTV whose IP address is 192.168.1.99:
http://192.168.1.99:57000/api/play/channel/7.1
Ironically, using Siri on the AppleTV remote itself with these voice commands doesn’t work, because tvOS just tries to launch an app, like the network’s own, DirecTV Stream or Fubo TV or whatever, in order to stream that channel, instead of recognizing your DIY Siri shortcut and actually invoking it within the personalized Channels client. I even experimented with alternate codenames for the same shortcuts. Siri on AppleTV refused to work with any of them.
These voice commands do, however, work very well via my iPhone, iPad, Apple Watch, and more recently, the HomePod mini too. All "hands-free." This functionality is very powerful and convenient, and certainly easier than having to remember channel numbers to manually type on a remote keypad all the time.