pfSense between whonix-cli & vm machine

I need to use pfsense between the whonix-gateway
and a ubuntu vm. The point is that can’t found a guide
to the proper config if needed.
I already know that whonix use Firewalld but I’m trying to do this just in case.

See:
a Proxy between Whonix-Workstation and Whonix-Gateway (Whonix-Workstation -> another VM -> Whonix-Gateway)

Not at time of writing.