Hi I've just installed ISPConfig according to the perfect setupt ubuntu 20.04 and I noticed that in the admin panel under System -> Firewall there are no records listed. The server is behind a router where the necassary ports are forwarded to the server so maybe no firewalls records in ISPConfig are needed?
That is correct, there is no firewall setup for you, you must add one yourself. As for your setup, if you are ipv4 only, you won't gain any additional filtering from the internet by adding a firewall in the ispconfig server. I would add it anyways. You do gain a layer of protection from other devices on the internal network, and it's just good practice to have that layer in place; plus you'll be ready for potentially adding ipv6 later, where you most likely will route public IP addresses, not use port forwarding.
