I don't live in a big apartment, but due to its construction kinks, the router sits on its one end and pretty much every network device I have on he other one. I solved this problem by buying a range extender and plugging it into the wall socket. For pretty much any network device including my laptop, this was enough to give me a high streaming speed.

Not for my Philips TV I bought this month, it seems. After a 4K YouTube video got choppy and switched to a lower resolution several times, I investigated and it seems its connection speed was ridiculously slow. Like, more than 10 times slower than my computer. This seems to be the case not only for the YouTube app – a speed test shows 60 Mbps and lower, sometimes even 10. For comparison, it's 200 Mbps on my PC, that sits farther away from the extender.

I'm not sure what could cause such problems. The signal strength seems OK (-48 DBm, -56 at least) and why wouldn't it, the extender is currently two meters from the TV and isn't obstructed by anything.