Genera might be the Common Lisp of operating systems (as well as the, or at least an, operating system of Common Lisp). Is there a Scheme of operating systems?

Genera was originally developed in ZetaLisp. Later Cmmon Lisp was added and many newer parts of the OS were developed in Common Lisp.

Yup. (Was that intended as a correction to something I wrote? If so, I wasn't clear enough and I apologize.)

Regardless, it may be worth adding that ZetaLisp was one of the most important "source" dialects from which Common Lisp emerged, and that Symbolics people were heavily involved in the process. Genera wasn't so far from being "an OS of Common Lisp" even before there was a Common Lisp.

The main difference: ZetaLisp was developed specifically as a language and its implementation for a certain type of Lisp Machines as an OS language.

Common Lisp OTOH is a domain independent Lisp standard with only very few specific OS-related features.