An older bug (https://issues.guix.info/issue/37662) discusses a similar issue, but for a foreign distro with Guix installed (not a native Guix distribution).
That bug mentions two things: - make sure that either ‘glibc-utf8-locales’ or ‘glibc-locales’ is installed (as root) - make sure that the GUIX daemon is configured to use a UTF locale so it can handle the UTF-encoded filenames in the nss-certs package. I'm not sure whether these issues apply to a native Guix distribution. What I do know is that when I encountered the error myself (running Guix on Debian 10) I needed one additional thing: the environment of the user installing the package had to include a UTF locale. After switching this environment from LANG=C to LANG=en_US.utf8, the package installed without issue.
