Linux zoom client sees USB audio, but no sound

[executorelassus]

I have a Focusrite Scarlett USB audio interface, connected through ALSA. The Linux zoom client (on gentoo, that's net-im/zoom-6.2.10.4983, though this has been a problem for several versions now) can see the device, but I have no input (from the mic) or output (through the headphones). Every other audio program I use -- ardour for sound recordings, video players, Discord, etc etc -- has no problem seeing the audio device and using it for both playback and capture. It's *just* zoom. So what's the problem here, and how do I fix it? I've turned off noise cancellation and set it "for music," none of which has helped. 

Cheers.

[storyhub]

Linux has all kinds of compatibility issues. Ardour is a DAW using open source code specifically designed for Linux, Mac, and Windows so not surprised that it works on Linux. As an audio engineer I use Fousrite 2i2s, 4i4s, and 18i8s on Windows with Zoom and it works flawlessly. For Raspberry Pis (a Linux like OS) I use specific add on hardware to accommodate XLR output that then can be connected to FM transmitters for radio broadcast systems or any audio mixer. ALSA still requires specific drivers. Also, Focusrite hardware is NOT compliant with Linux https://support.focusrite.com/hc/en-gb/articles/208530735-Is-my-Focusrite-Product-compatible-with-Li...