This package does not support Python 3.12. Please test it with Python 3.12 as a matter of urgency as the default will change in early June, as per message on gentoo-dev: https://www.mail-archive.com/gentoo-dev@lists.gentoo.org/msg99104.html. Please check the information provided in the tracker. Ask in #gentoo-python on IRC if need any help.
Fixed with commit https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=d997005efaa60f8be238436c4f12655e3955bb0e app-arch/unrpa: enable py3.12