It's only for Android TV devices. Ordinary Android devices (phones, tablets, etc.) aren't supported. I tried running an Orange Pi 5 on one of my TVs with the build of Android (not Android TV, just Android) that's available for it, but it wouldn't run the Apple TV app. That's when I switched to Chromecasts for both of my TVs.
The 10-foot experience with the newer Chromecasts is objectively better, IMHO. Instead of farting around with your phone to control it, it has a proper remote control that can also be set to control power and volume on your TV (or your AV receiver, if you have one of those). I had previously run OpenELEC on Raspberry Pi 3s controlled by Playstation 3 Blu-ray remotes, but the WAF of the Chromecast is higher with access to more video sources.