This app lets you add custom HLS/m3u8 files or use existing ones to a list which then compiles all of those files into separate live channels on Android TV's Live Channels app.
Cumulus TV uses a simple JSON interface for adding this data and can be synced to a file in Google Drive to make editing channels really easy. (You don't want to type in a long URL on your TV!) You can set a channel name, number, and logo for each, and the system plugs into the Live Channels app without hassle.
Found a bug or want to suggest a recommended stream? Check out the project on GitHub: https://github.com/Fleker/CumulusTV