Even worse, the ENOB is closer to 9 bits in testing. It’s got horrible DNL/INL. Totally worthless for any audio unless you’re trying to do chiptunes or something.

FWIW, this project is entirely digital (audio in: USB, audio out: S/PDIF or I2S).

There are other projects for the Pico which implement S/PDIF in.

In either case, since it is digital, the quality (or lack of) of the internal ADCs should not matter.