Missing LAN ports on ASUS GT-AC5300

Installing and Using OpenWrt
1

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?

Marc

2

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.