I am using the bespoke image for Raspi 4 for my Channels DVR server which works great.
Looking at the various options for the client side, they all seem to have some drawback or other often caused by the demarcation between the hosting OS and the Channels app. I've struggled with IP control of the app on my Nvidia Shield as some commands have to go to the OS and some to the app. I believe the Apple TV OS doesn't allow for numeric entry at all and IP control is very difficult.
So that got me thinking, what about a bespoke image for a Raspi 4 client? Channels would then have total control over the whole system. IR input using a Flirc, IP control via the API over the whole system and HDMI out to TV, AVR whatever.
Maybe there are a million technical reasons why it wouldn't work, but if it is possible, I'd certainly much prefer that option than an app running on someone else's hardware and OS. No worries about the hosting OS updates causing issues, it would all be under Channels control.