If you live somewhere that’ll let you then access to a crawlspace like an attic will let you do this

For example at my place getting into the above house crawlspace lets me access the insides of my walls from above. Simply run Ethernet from above where you’ll want each end of a plug to be, then drop it down and put it in place through a cheap (like .45c) Ethernet wall adapter. Hardest part is cutting the hole into your wall for said wall plug

I’m simplifying a bit but honestly it’s incredibly easy to buy a length of Ethernet wiring and some rj-45s, Google how to wire them, and run it yourself. I ran a short wire across a room once and it only took like an hour. Would be less in future now that I have experience