OpenBSD has a "netiquette" doc for its mailing lists: https://www.openbsd.org/mail.html

Not sure if you want to count it as a "code of conduct", but it certainly defines rules on how to communicate and contribute to the project.

I'd count it as one in the general sense I'd count the style(9) manpage as another, not in the specific sense I indicated I was referring to:

> ... fine without a code of conduct — in the sense bakugo employed "code of conduct," not in the generalized sense ...