How do I expose public IP to LAN or WAN Port

I have GL iNet GL-X750 SIM Router. Can I expose the public IP from the SIM modem to one of its ethernet ports?

I want to use the SIM router as a modem only - I dont need the DHCP or NAT. I have a mesh network router (DECO X60) connected to the SIM router LAN port. The LAN port outputs a NAT IP (192.168.1.x), and my DEC0 X60 also assigning a internal IP to whatever device conntects to it. How can I avoid this double NAT situation? It is cutting my speed in half due to extra hops

In summary: I want a public IP on the SIM Router's LAN Port.. And the LAN Port with public IP should be connected to my home mesh routher 's WAN. Is this possible with openWRT? I have openWRT firmware in the GL-X750 SIM router from the rOOter Project.

If you use one of ethernet emulation modes as opposed to ppp emulation you just bridge sim port with lan port and use dhcp pushing all openwrt stuff silent.

Please post

ubus call system board

for more accurate instructions.