What you have described are the limitations of the built-in HA Spotify integration.
You might want to check out my SpotifyPlus integration, which is a direct replacement for the HA Spotify integration. It can be installed via HACS, or manually. You can also keep the HA Spotify integration installed, if you want to compare them side-by-side.
Your USB connected DAC should be recognized, if it’s a Spotify Connect enabled device (if the HA Spotify integration recognizes it, then SpotifyPlus should as well). Note that Google Chromecast devices are not supported by SpotifyPlus.
Quick Example - Transfer playback to the “Office” Spotify Connect Player device name.
service: spotifyplus.player_transfer_playback
data:
entity_id: media_player.spotifyplus_john_s
device_id: "Office"
play: true
More Information Links
- SpotifyPlus GitHub Project Wiki Home
- SpotifyPlus GitHub Project Wiki Media Player Service Enhancements
- SpotifyPlus GitHub Project Wiki Services Provided
- SpotifyPlus GitHub Source Repository
- Install Instructions (via HACS)
- HA Community Forum Support
Hope it helps!