If you live in the US and your house was built in the past 20 years or so, check if you have old school phone jacks around. Many contractors took a “short cut” and ran dedicated cat5 cable to each of those wall ports instead of daisy chaining cat3 (probably was cheaper to buy cat5 in bulk).

Take the face plate off your phone jack and if you see a wire with four pairs of wires inside, only two connected to the jack, you may be in luck. I had rented a few townhomes which were like that, enabling me to build out a simple wired network without modifying or drilling at all.