I would like to administer my firewall by good, old-fashioned iptables commands saved by iptables-save instead of ufw or firewalld. For RHEL, there is a neat little package called iptables-services that does just that. (See here) For Debian, there doesn't seem to be one.
I just could slap iptables-restore </etc/default/iptables into /etc/rc.local and leave it at that, but I'd like a cleaner setup. If it can come as a systemctl unit it'd be ideal.
You might want to have a look at iptables-persistent.