@sksos, I edited my post to correct M21 to M12. Your clarification is duly noted.
If having both LAN and i2S inputs is not standard, and an additional input was added by machining the rear plate and adding an i2S card, then I consider this customization. You might consider it upgrading. I think it’s semantics. The take-away is it’s possible for a fee.
Had this been offered when I updated my M1 SE to M1 Series 2 a year ago, then I would have done it.