As described in https://lists.ipfire.org/pipermail/development/2020-January/006883.html , it is not possible to create a firewall rule in the WUI with both source and destination port limited to a predefined service or service group. Since limiting source ports to values > 1023 is a common (and primitive) technique to detect/block traffic from compromised services running on privileged ports, this is a major usability. Suprisingly, nobody seemed to notice it until today.