I started looking into it for radio - unifying paid SiriusXM, free TuneIn, and free Shoutcast/Icecast powered radio stations, in a single system.

My idea was to show a list of our favourite radio stations on a dashboard tablet, with buttons to play them on particular media players (Google speakers, etc)

I set it up and started making a Home Assistant dashboard that shows the list. It took a while to figure out how to properly display the list of all the stations, but I ended up figuring it out using the flex table card component: https://community.home-assistant.io/t/dynamic-buttons-based-on-template-sensor/917207

I didn't end up finishing the project though, and put it on hold while working on other things. I'll revisit it one day.

It can also pull from Plex, but I haven't tried that. At the moment, I usually cast from Plexamp to my speakers when I want to play something.