Brand new setup on CM4 with DUAL-ETH-BOX-A montherboard and case.
Had firewall software before and both ETHx ports were used - so its not the hardware.
port 1 (eth1) entering forwarding state indicates that the eth1 (WAN) interface is active and is now forwarding traffic as expected.
You can check /etc/config/network to confirm that eth1 is set as the WAN interface. By default, eth0 (LAN) is used by USB devices, and eth1 is tied to the internal port for WAN (bearing in mind this firmware is for Pi4 and not officially CM4 although have had reports of it being used successfully)
For LuCI or SSH, the default IP is 192.168.3.14, username root and password is whatever you set during first-time setup with the app.