Maybe start by omitting the part in the first paragraph about how it acts as a USB sound card. :)

I mean, I know what you meant, but that's pretty misleading phrasing for many people.

It's not much of a stretch to think that most people interpret a "USB sound card" as a thing with analog audio on one side and USB on the other side. But other than the subwoofer output, we don't have any analog IO on a Pico running this firmware.