Thank you for the lightning fast response, Stéphane. I can confirm that manually installing the cdrtools package using emerge -1a app-cdr/cdrtools solved my problem.
Gentoo ebuild version 0.5.1-r1^st(05:26:15 AM 02/12/2024)(nls -apparmor -fuidshift -verify-sig) might indeed need to be updated with an additional dependency.
Hmm, cdrtools should be naturally pulled with qemu, but I see with use flag configuration this can be missed. I’ll add an explicit opfteature note and document it in our wiki, thanks for pinging me!
(Offnote distrobuilder should probably depend on it unconditionally)