That Radio Player is an HTML5 webapp that uses the <audio> tag to stream (web) radios on a mobile phone. It has been originally developed for Safari on iOS 4.3 but I updated it for iOS 13.3.1. It is optimized for a mobile phone screen but also works well on an iPad or on macOS using Safari. I haven't tested other web browsers.
Try That Radio Player on your iOS device: https://romaindillet.github.io/that-radio-player/
This webapp is written in HTML, CSS and JavaScript. No code is executed server-side.
If you want to run your own version, you should first edit the radio presets to replace .m3u8, .m3u, etc. links with direct links to the streaming servers of your favorite radio stations.