My unifi I put upstairs. But I changed my router to Asus router, so signal should be stronger. So far no problem using 5Ghz wifi from downstairs (on phone and laptop).
Yeah, now I know, only after buying the TV. If I had known, I would have bought a different model TV that supports 5Ghz wifi.

I'm thinking of buying a router extender(?) (i dont know what that thing is called). Basically I put another router (Router-B) next to the TV. This router connects to 5Ghz wifi to my upstairs router (Router-A), and I connect my TV to this Router-B using cable. That way I can get 100mbps via the 5Ghz wifi, right? Is this possible? What is the thing called? router extender? router adapter? Is there such a thing that will allow this?

I foresee a similar issue as TS...

Wanted to stream 4K with 5G wifi (in future maybe the speed will required more than 25MBps)

my TV is SONY KD-55X7000F  --> built-in Wi-Fi 802.11b/g/n (don't have 802.11ac)
Roku Streaming Stick+ --> built-in 802.11ac (its one of their feature with WIFI Enhancer)
TP-Link AC1750 router --> 802.11ac
OK question is, if I HDMI-plug my ROKU S+ to my TV and connect to my router with TIME does it make my Netflix streaming under 802.11ac bandwidth now? kinda like bypass the Sony TV built-in WIFI?