A 5 port 2.5GbE switch would upgrade this to 5 total ports (4x 2.5GbE), and costs less than $100. If you only need 1GbE then it's even cheaper.
Outside of home-labs, it's rare for me to see any devices connected to the LAN side of a wireless router these days, and more than 1 (i.e. the non-portable device that is closest to the router) is exceedingly rare.
Chaining a switch off the gateway is the best way to do it anyway. If you do that, then when you reboot your gateway, your lan devices do not lose their physical link and can continue talking to each other.
>Outside of home-labs, it's rare for me to see any devices connected to the LAN side of a wireless router these days
I would assume every gaming desktop computer would be? I actually assumed every desktop would be...