I have a longstanding wireless connectivity problem which occurs usually around 19:00-21:00
I have no idea how and why this is happening. Wifi becomes unstable and incredibly slow.
I'm suspecting my brother's LG webOS smart tv
I have no specific insights but if you suspect a particular device is causing the problem, you can test that by waiting for the usual time you experience the problem and not using that device.
What device? What version of OW are you using? What is the CPU load when that device is pulling the bandwidth?
How fast is the data plan you have from your ISP? Is 130 Mbit/s maxing that out?
Do you have a wired device you can use to test internet responsiveness and speed while the device is drawing that bandwidth? At least isolate the problem to one of the wifi and not the connection itself.
Always set your country in the radio config for best wifi results.
The first and second devices apparently only have one RF chain which limits them to MCS 7 at 72 Mbps. The TV has two RF chains so it can use MIMO to realize double the speed at MCS 15.
Actual throughput to a device is always less than half of the raw radio MCS speed.
Signal levels look good. Do some scans to see what channels the neighbors are using and set your channel to one that doesn't have any strong neighbors. The auto setting is supposed to do that but it may not always work.
Also test ISP speed during peak times. Like darksky asked, what type of Internet connection do you have and what is the rated speed?