The directory /usr/lib/cups doesn't exist as cups is installed to /usr/libexec/cups.
The sudoers.d and backend-available directories will be created if they don't exist.
Also Gentoo Linux either uses openrc or systemd as init system so I've added rc-service cupsd restart and systemctl restart cups.
The directory
/usr/lib/cupsdoesn't exist as cups is installed to/usr/libexec/cups. Thesudoers.dandbackend-availabledirectories will be created if they don't exist. Also Gentoo Linux either usesopenrcorsystemdas init system so I've addedrc-service cupsd restartandsystemctl restart cups.