I'm trying out Virtualmin on a Debian 9 VPS. I typically do not use control panels and have done everything on a VPS simply with SSH.
I had a working prerouting rule that seems to be overriden by Virtualmin. It is saved in the rules file and shows up in the Linux Firewall tab, however that tab says:
Warning! It appears that FirewallD is being used to generate your system's firewall. Maybe you should use the FirewallD module instead.
I poked around FirewallD and don't want to use it. How do I disable FirewallD and instead use Linux Firewall / iptables without breaking Virtualmin?