Theoretically one-shot service that launches a shell script with systemd run on boot could do the trick. OTOH it's probably easier to just write a tiny service

Theoretically one-shot service that launches a shell script with systemd run on boot could do the trick. OTOH it's probably easier to just write a tiny service at that point. Generally results of -run services can be captured through journalctl, so it's possible to run systemctl show on them and get the config.