Peplink will need to add WAN static routes to properly support Starlink terminals.
An Outbound policy will send the packet to the MAC address of the default WAN router. If the out of band management interface uses a different MAC address, then it will not see the traffic. Starlnk and other DSL modems use seperate MACs and therefore need a static route. DOCSIS cable modems seem to use the same MAC address and therefore an outbound policy is enough.