Hey there Sunguard,
I apologize about the late response, thank you for being patient! Were you able to fix that audio issue? If not, I'd be happy to help out, let me just ask you some questions about what's happening:
I look forward to your response, and if you have any other questions or concerns for me, please let me know!
I have a similar issue that only just started this week where I used to be able to listen to audio through pc connected headphones while watching cast tab on tv. Now cast tab will only play audio and video through tv but cast desktop will let me listen through headphones and watch on tv
I tried a bunch of chrome://flags suggestions from way back most of which dont exist anymore. The issue started when I switched to windows 10. I dont see any additional device to change as default. Previously when I casted desktop to chromecast the sound on the computer got muted. Now either they both are muted or arent.
I'm really sorry about the late response on this, but I talked with the engineering team about this, and it seems like that it is actually working as intended. Cast Desktop follows the actual source, which would mean that if the device is muted, the Chromecast would play no audio. It seems there were flags in the past to override this, however, these flags are no longer found with the last Chrome version though.
I'm sorry I couldn't have found a "fix" for this, as it is working as they designed.
We haven't heard back from Sunguard, and it's been a few days, so I'm locking the thread. As always, feel free to make a new thread if you have any more questions or concerns.
Have a good one!