Darn, it's never easy.

So annoyingly it seems that ScalablyTyped has convoluted the stUseScalaJsDom to refer to not just scalajs-dom but also all the types in the SJS standard lib (e.g., js.Error, Uint8Array, etc.). So these all had to be switched to its own generated facades for those.

Are we shading the SJS standard library now? Does the resulting artifact remain interoperable with folks using the SJS standard library?

Are we shading the SJS standard library now?

Not really. There's just another set of facades (under our internal namespace) for the same underlying Javascript types. At the Scala level these appear to be unrelated classes, even though they are modelling the same Javascript types.

See for example this line which converts between the SJS std lib facade for Uint8Array to the ST-auto-generated facade for Uint8Array:
https://github.com/typelevel/fs2/pull/2681/files#diff-98450717b1764f56ec34f86f4c240563625aa001a68b64f062ec827c8ffe342eR36

Does the resulting artifact remain interoperable with folks using the SJS standard library?

Yes. In fact, we're still using the SJS standard library ourselves. This change affects only how we interact with our internal, private Node.js facade.