Universal Remote Card - adding custom element to launch a source

Configuration
1

I am trying to build a custom button. I have this currently working as a script and then assigning a button to the script.

sequence:
  - alias: Launch Root Sports on Apple TV
    sequence:
      - data:
          source: ROOT SPORTS
        action: media_player.select_source
        target:
          entity_id: media_player.great_room_3
alias: Launch Root Sports on Great Room
description: ""

but I’m failing to adapt it for Spectrum TV app.

Any ideas? I assume I just don’t know what to list as the source… but I don’t know. if it is just a matter of knowing how to list the source for apple TV is there a way I can definitively know without just blindly checking?