I rent an apartment with double brick walls everywhere. I cannot install cabling in the wall, or really anywhere it's not a severe trip hazard. For the most part, this is fine, because almost every device I own that requires internet access has wifi. (The few that don't, like my NAS, can live next to my networking equipment.)
Your suggestion would have meant that I couldn't connect my Playstation to the Internet, which is a little bit silly, especially given that my scenario is not an uncommon one.
Powerline adapters are pretty cheap nowadays and fast enough. I get synchronous 200mbps over a pair of TP-Link gigabit ones in a place with really poor quality wiring, and they come with power pass-through so I don't even lose a power socket.
I do use a powerline adapter and it works but I'm afraid that there aren't too many eyes looking at them - what if they have a big flaw and it stays dark?
There's no way these adaptors aren't vulnerable, given the nature of them. In my opinion. Extracting the signal from the mains and feeding it into GNU Radio for demodulation, then subsequent attack, would be an interesting exercise.
CAT5 and duct tape are your friend. I have the same problem and it’s quite easy to manipulate it around and behind things without problems. One section of cable I have is 19m to span a 3m floor.
We have to do this because I live in crowded London and WiFi barely works when you have 40 other networks next to you.
It's certainly not aesthetically pleasing, although there is some mileage in that department with printed duct tapes, but it works which is the main thing. To be honest with careful routing it's only taped down in one place in a corner. You wouldn't know there were any cables running around unless you look very carefully.
Your suggestion would have meant that I couldn't connect my Playstation to the Internet, which is a little bit silly, especially given that my scenario is not an uncommon one.