Was-Working: In Ubuntu 19.10, I was able to switch between my USB headphones and HDMI/DisplayPort based sound output whenever I wanted, and each would work depending on the setting in System Settings -> Sound.
Problem: Since the upgrade to 20.04, while my USB Headphones are plugged in, ALL sound goes through them, even if I select HDMI/DisplayPort as my output device in System Settings -> Sound.
Work-around: If I simply unplug my USB headphones, I can get sound working through DisplayPort as normal. However I don't want to always unplug my headphones.
The way everything is hooked up is, my monitor is connected via DisplayPort to my Nvidia GTX 1070 card, and I have audio speakers (3.5mm jack) hooked to my monitor. If my audio device is set to DisplayPort output it should play through my speakers, as it was doing fine in 19.04.
Nvidia Driver Version: 440.100.
paprefs
to get this option. I see the new "virtual" device which says output to X, Y, and Z (all audio devices) but sadly, the USB headphones are still "clobbering" everything else even when I select that simultaneous output device. Perhaps there is something else going on which is auto-muting everything else when the USB headphones are plugged in.