There's definitely a bug - I think the receiver software for subsonic (the main web UI) is not working anymore (probably out of date to latest protocols). I'm seeing the submarine icon show up, but it doesn't start playing after that.
SubFire M2 chromecast is still working, both off of phones (it can be added as a ProgressiveWebApp) and in the browser.
https://subfiresuite.com/m2/ or
http://subfiresuite.com/m2/, depending on if your server is secure or not. It uses the default built-in receiver.
update - partially working. I'm not getting time updates from the device, which means it doesn't necessarily figure out when a song ends and it needs to flip to the next track.
However, it does require the subsonic license to use apps.