Ethernet

I'd start with a new router that has plenty of inputs.

Thanks , but that wasn't the answer to my question. 

@zappas 

I’d start with a new router that has plenty of inputs.

Now, unless you can explain why that isn’t responsive, this seems to be the best option.

@zappas additional details on your set up need and what you are using the ports for would be helpful. If you want to keep your router then buy a multiport switch to plug into one of the ports. I had the same issue on my prior router and bought a $20 TP link switch that worked fine. It’s installed next to the router away from audio systems. I used it for non music function lines. Solar, office computer, gaming..the other port I connected my mesh system which had my music server and the mesh units connected to my audio systems. Now i have an upgraded modem/router with 4 additional ports. I use the ports for 1 switch, 2 music server, 3 mesh. Both worked/works for me but I prefer having my server plugged directly into the router now.

If it's a router/cable modem you'll need a multi-port switch.  $60 or less. I'd recommend you go with a fiber converter just for surge protection.