Line 128 of /etc/init.d/udev has /lib/udev/write_root_link_rule which is missing and causing breakage. Please update or block! Reproducible: Always
It looks like your /etc/init.d/udev is outdated, use dispatch-conf or etc-update to merge a new one. None of >=sys-fs/udev-init-scripts-16 init.d/udev call write_root_link_rule. Older versions do, but that's why udev-195 has a !<sys-fs/udev-init-scripts-16 blocker.
Comment #1 seems to be accurate, there is nothing to be done here, closing off