you mean you haven't heard of /etc/grub.conf.d/entropy.d/randomseed.d/grub-entropy-randomseed.conf and it's good buddy systemd-enable-grub-conf-d-entropy-d-rand

you mean you haven't heard of /etc/grub.conf.d/entropy.d/randomseed.d/grub-entropy-randomseed.conf and it's good buddy systemd-enable-grub-conf-d-entropy-d-randomseed-d.target ?