Actually, I just tried it and updated my trial subscription to Superstar. It charged me 66.99 then as a result. My loss I suppose
So your chromecast feature works but its laggy. I realise you’re tying it into the alsa stream and that will let you integrate it with any audio source you can stream in from external streaming services as well as audio inputs that the device could support. But when you pause or change a track, the stream reaction to this is delayed and noticeable. You might get gapless playback but after that it will feel unresponsive to many.
My recommendation for playback of specifically local/LAN/NAS audio files would be be to try and host the file from its mount point in Volumio and cast a URL directly to the chromecasts and do what I did in mpd2chromecast. Then by matching local playback, play/pause/skip etc to near instant controller actions on the chromecasts. You could then mute local playback totally. People using Chromecasts for Volumio playback will get this… you play locally via your DAC or you play via a single selected chromecast or cast group.
You should also remind yourself that any streaming service worth its money will make a direct integration with Google Cast from their own apps. So who really needs to use Volumio to play Tidal back via Chromecast?
So the gain IMO with Volumio and other streamers should be to target external streaming sources (Tidal, Qobuz, Spotify etc) for local playback via HDMI or attached DACs. Then things like Google cast support is best reserved for playback of attached/network storage only.