I've also found some flatpak radio packages. Should I disregard radiotray and try any flatpak radio application?
What I liked of radiotray is that it was minimalist, simply click on it, choose a radio station and that was it, I didn't need to open a whole suite just to listen to radio online. Adding station was also very easy, just pasting a url.
I recently tried shortwave (flatpak) and it works pretty well. Let's you search for public streams, and if the radio stream includes song data, it even auto records individual tracks for you if you want. Pretty minimalist and functional
When I open your link for radiotray-ng, it says, "ebruck released this 2 weeks ago." You'll also notice if you go to the Releases page, it doesn't show the year for the current year, but does for past years.