There will also be an official plug-and-play custom board that includes all of the relevant IO, connectors and codecs.
I had a project in mind that was waiting for something like this! :)
For 2.1 configurations in a pinch, the firmware includes a software DAC that's more than adequate to drive a subwoofer, so only one external DAC is needed.
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.
It is not 100% plug and play as you can choose your own software.
A custom board sounds great, too.
Since a Raspberry Pi Pico doesn’t have built-in audio output ports, I think the main thing blocking ordinary people from using it is figuring out the hardware? A link to a tutorial for how to add audio output would be useful.