$ gpkg-sign inkscape-1.2.1-r2-1.gpkg.tar !!! flock: cannot open lock file /run/lock/portage-binpkg-gpg.lock: Permission denied * Signature exception: inkscape-1.2.1-r2-1.gpkg.tar I think it wouldn't be unreasonable to make it work as non-root ;-).
You can set the lock to somewhere that allow read/write in make.conf BINPKG_GPG_SIGNING_BASE_COMMAND="/usr/bin/flock /tmp/portage-binpkg-gpg.lock /usr/bin/gpg --sign --armor [PORTAGE_CONFIG]"