As far as I know the LAN is 1 G port 0, WAN 1 G port 1 on a factory new device. You need to do basic setup and then switch ports if you want to use SFP+ for LAN.
Alternatively connect a console cable and assign the network interface on the text console.
The interface assignment is fixed. The LAN interface is only on the 1 G port labelled "0". OPNSense does not have a builtin switch treating all ports the same. These are all individual routed interfaces. All other ports apart from "0" and "1" are inactive on a factory new device.
You don't have a speed/duplex problem at the moment. You can only access the UI on the port labelled "0". That is by design. You cannot use the 10G port for the UI at the moment.
Sorry, mate, but ...That's why I finally added the picture.