Are you using the standard xattr command that’s built into macOS? IIRC there’s another program out there by the same name with completely different syntax. Try running type xattr; it should say something like “xattr is /usr/bin/xattr” if you’re using the standard one.

I’ve also been watching CtC quite a bit for the last couple of years. Unfortunately, they’ve lately been doing a lot of long, highly technical puzzles, which I don’t find as interesting (though their shorter videos are still good). If anyone’s interested in checking them out, I’ll recommend a couple of older videos that I really enjoyed:

• “The Sudoku Miracle” set by Mitchell Lee has just two given digits, and some inadequate-seeming rules.
• “Everything is Wrogn” set by DiMono has pretty much every rule in the book, and requires that the solution violate all of them.

If you enjoy watching people solve sudokus and other puzzles, I’ll also recommend Rangsk (generally does the daily NYT hard sudoku, a 6x6 intro-to-nonstandard-rules “sudoku adventure”, and a collection of wordle-ish (but not not actually wordle) games), Bremster, and zetamath (does quite a few live solves with audience participation, as well as reaction vids to other people solving his puzzles).