I have this working to launch the Apple TV remote with shortcuts. Essentially you create a shortcut on your iphone that launches the app you want. For the Apple TV remote you can even specify which Apple TV to connect to if you have multiple units.? On the Crestron side, use the URL like normal except the path needs to be:
shortcuts://run-shortcut?name="whateverYouNamedYourShortcut".
In my case I named the shortcut launchremote so my full url is:?shortcuts://run-shortcut?name=launchremote.
