This is a system miss-configuration...
I'm afraid I cannot help "from afar" and I would need to get my dirty hands in your system to solve this issue (which is not actionable on the viewer coding side of things).
Sadly, Linux audio configuration is (and has always been) a total mess and a genuine PITA (for example I spent a full week fiddling with my first Zen 4 on an ASUS motherboard, due to the latter only exposing the USB audio interface, and had to write a non-trivial ALSA configuration file to get the audio playing both on the loud speakers and the headphone)...

Your best bet is to ask in your distro's support group/forums for help with WebRTC/ALSA configuration.
The ~/.asoundrc file should hold:
Which the cool_vl_viewer wrapper script will add when missing. Else, WebRTC cannot get the device names.