When I cast my music to a streaming device such as a chromecast or Nest speaker, certain aspects of the music controls stop working, others keep working, and others kind of half-work.
The playback functions I set to buttons do not work at all. They provide haptics, but don't launch any action.
The track title displays.
The track artist does not display.
The countdown timer I have continues to work.
The progress bar continues to work.
It will show the album artwork, but it has letterboxing and looks like a video thumbnail rather than album artwork. I have it set to open the current music player, which still works as intended.