How to utilize Ethernet throughout my house
Edit: My answer is targeted to the very little information posted at the time. The question is could this work, not what's the best way or fastest way.
Cat 5 cable and RJ-45 jacks have eight wires.
100 Mbps Ethernet uses two pairs (four wires), one for send and one for receive.
Telephones use two wires.
Therefore, you can run both ethernet and telephone over the same wire, and still have two wires left over. It all depends on how your home was wired. The outlets may need to be reconfigured, but it's easy to test if you can find the junction box and see if you can plug in an ethernet cable from the modem. If it works, problem solved.
The caveat is that the maximum speed under ideal conditions is 100Mbps. The actual speed might be lower.
Good luck.

https://www.instructables.com/Hack-your-House-Run-both-ethernet-and-phone-over-/