There might be, an ugly one. It depends on whether the Starlink accepts packets from devices that have their 192.168.1.x addresses assigned statically rather than obtained from the DHCP server in the Starlink terminal. Can you check that, please? I.e. configure an address from that subnet statically on your PC, connect it to the Starlink, and try to download or ping something in the internet.
If it works, the following would be the next steps:
- assign some unrelated address&subnet to the WAN interface of the router (the one that will be connected to Starlink) - let’s say 192.168.33.2/24, and set a default route with a gateway address within that subnet - 192.168.33.1
- create a static ARP record, stating that the MAC address of 192.168.33.1 is the one of the Starlink interface (you have to find it it in advance if it is not on the label on the Starlink terminal)
- set the arp parameter of the WAN interface of the router to proxy-arp, so that when the Starlink interface sends an ARP request for an address from 192.168.1.0/24, your router responds with the MAC address of its WAN interface because it has 192.168.1.0/24 on another interface
- add an action=src-nat rule with to-addresses=192.168.1.N that differs from any address assigned by the Starlink’s DHCP server (no idea whether there is a range within 192.168.1.2-192.168.1.254 from which it doesn’t assign addresses to DHCP clients).
It will not be compatible with another IP configuration on the combo port (because whenever the combo port is up, the default route will become active), but it should allow you to use the 192.168.1.0/24 internally and still use the Starlink as an uplink.