N.B. you should only do this if the WAN interface is actually on a protected network!
Set up a new firewall rule on the WAN:
- First section should be Pass, WAN, IPv4, TCP
- Source: Restrict as appropriate (note – need multiple rules if wanting to allow multiple subnets through).
- Destination: WAN address
- Destination port range: HTTPS (443)
Note that if your WAN network has private addresses on it then you also need to configure the WAN interface to allow this (bottom of configuration page, uncheck Block private networks and loopback addresses). Note that you will then see this rule removed from the firewall WAN list.