My Mac Mini's Preferences > Sound window lets me “select a device for sound output.” This works well driving my sound system. It detects other devices but lets me select my converter:
    USB > Digital-to-Analog converter > mixer board.

Everything I find online seems to indicate that nobody’s created a similar configuration tool for Linux, that we have to use some queries and build a config file. The query I tried did show that there are two devices, but I really don’t know what I’m doing.

Any instruction would be greatly appreciated.

My situation:

In my Mint system, I want to drive a monitor via HDMI,
and sound via USB > Digital-to-Analog converter > mixer board.
The very same connection worked when driven by the Mac Mini.
Linux never had a problem with it either, but I messed up something.

At one point the sound was playing through the monitor’s relatively weak loudspeaker.

After some tinkering, nothing is coming through.

Thanks,
Victor