sys-apps/renameutils-0.12.0 seems to compile and execute just fine on arm64 (Raspberry Pi 4 64-bit) (submitting a bug report as suggested in https://wiki.gentoo.org/wiki/Knowledge_Base:Missing_keywords_and_keyword_requests#Resolution )
Unable to check for sanity: > no match for package: foo/bar
Remember to update the package list. Please *do* file keyword requests for stuff that you use (ideally don't for stuff you don't use though).
~arm64 added, closing