Thanks for posting in the community and apologies for the late response.
While channel buttons are not available on the Google Home app. You can send us feedback by saying "Okay Google, send feedback" followed by your message. Also, you can check out this link for more information on how to use your phone as a virtual remote control. I'll consider this thread as complete and will lock it after 24 hours. If you have more questions, feel free to create a new thread.