Hi, I think Chromecast devices should be able to be paired like in Google Home to enable stereo. The implementation of this addition could be set up in Home Assistant entity groups.
I think that’s a Google function, You pair them up in the google home app if I remember correctly.
Yes. It’s done in home
So what OP is looking for is someone to write an integration to allow Chromecast to put out sound in stereo with separate speakers.
Nothing is impossible, but short of Google doing it, that’s pretty close.
I suggest buying a couple of cheap Google Home speakers.