Doesn’t matter. That’s why it’s called “Common” Lisp. Any code will run on any conformant CL.

Fair point, but in the specific case the differences matter indeed. StumpWM is coded and extensible in Common Lisp, while Emacs use Emacs Lisp and Guix is built on Guile Scheme - both not CL conformant.

it's a very lispy stack, otherwise!

Ah. Yes. Right. But these aren’t Common Lisps. But you’ve indirectly brought up another useful point, to wit, the general Lisp paradigm is so useful that language designers regularly approximate it when building new platforms. (Clojure is another.)