I have been recently been using two Chromecast Audio dongles as virtual Squeezeboxes with Logitech Media Server and the CastBridge plugin to make it possible. When the dongle is used as a transport only optically connected to an external DAC they are excellent (limited by the DAC). The Chromecast's own DAC is OK, but you must remember to turn off the dynamic compression (that is off by default when an external DAC is used.)
They are remarkable devices and I am sorry Google no longer make them.
Brian
In Southampton: Raspberry Pi 4 running PiCorePlayer, Beresford Caiman SEG, Quad 77 Int Amp and CD Player, AVI Neutron 4, Sennheiser HD25 headphones.
In Nicosia: Small Format HTPC, Beresford 7520 ,Quad 405-2, Quart 980s German Tower Loudspeakers.