Missing LAN ports on ASUS GT-AC5300

I just installed OpenWrt 21.02.0 on my ASUS GT-AC5300.
It is a router with 8 LAN ports and 1 WAN port.
However, in the configuration it only has 4 LAN ports (lan1, lan2, lan5 and lan6) available.
The WAN port and the 4 remaining LAN ports (lan3, lan4, lan7 and lan8) seem to be missing.
Could somebody explain how to make the missing ports available?
Or are these simply not available in OpenWrt?


I would like to replace the main router with this, but the wan port isn't available.

This router is a great hardware, 1.8Ghz quad core, 1gb ram, 256mb nand.

While my EA8500 takes 19s to start the adblock, the same config on my GT-AC5300 takes only 8s.

Any help to fix the missing ports are welcome.