Does the audio/speaker USB device show in “lsusb” (from the CLI/terminal)?
Does it show up in “Settings” (Settings > Sound)
at “Output Device”?
This computer (the screenshot source) only has one possible output when clicking on the select list for “Output Device” - but my other computer can have several, my USB3 Hub/Soundcard, my HDMI/Displayport output from my NVidia PCIe GPU, or one of two other USB audio devices (Jabra headset, and or Logitech headset via USB tranceiver).
If it’s not showing up in Settings > Sound > Output Device, I’d suggest you’re out of luck and it’s not compatible with your Ubuntu 20.04 installation.
During all this covid19 working from home stuff - I do this about a dozen or more times a day (Settings > Sound > Output Device / Input Device), having to switch audio output device and microphone source for Teams or Skype or WebEx or Bluejean meetings… And today my family all went out - so I switched to the HDMI/Displayport output device, which is wired out from my Lenovo monitor to Logitech 5.1 speaker setup, so I could crank up some loud music, extra loud, @ “eleven” on the volume dial 
…