I'm not sure about your configuration, but most routers I've seen have a cat5 socket for extension, and a few normal cat5 sockets. There is a cable called (I think) a "null modem" cable, usually bright yellow. It allows you to connect one computer to another via cat5 without a router. You can also use this type of cable to daisy-chain routers if the extension socket is not available. All it is is a cable with the Rx/Tx wires reversed.
The WiFi router supplied by my provider only supports 2.5 Mb/sec over WiFi, but 5 MB/sec over a cat5 cable connect. So I just daisy-chained a second router I had laying around that did 5 MB/sec over WiFi and had greater range, using the extension socket and a normal cat5 cable. I could have also done the same thing using using a null modem cable plugged into a "normal" socket on the provider-supplied modem. I also have a cheap ($15
https://www.tmart.com/300M-Wireless-WiF ... 55269.html) WiFi repeater that extends the range into my garage. -50dBm throughout the house and garage.
I know, I know, those are pathetic speeds, but via DSL because of my extreme rural location in a county with only 4 stoplights (nearest 60 miles away), but 5 legal brothels.