Dear TS,

let me share what I know about 5Ghz wifi, others /k also can share share
Sharing is caring.

I'm using ASUS RT-AX88U almoust (1.9K +++ few years back.)

1) not all wifi device are compatible to new 5Ghz protocol, (especially some older device)
so some new device also only support 2.4G, please refer to their manual.
2) my router 5G also giving problem gila-gila one. After power on, 5Ghz work fine, after 1 week ++++, 5Ghz fuck up. ( I dunno why)
after I power off and on again, 5Ghz work fine again.
so to resolve this I set timing to off and on 5Ghz (act like a reset). (refer to photo below.)
now everything work like what I want.
SET TIME

Difference router lain interface. refer to your router manual or provider. (don't ask me where to find set timer, don't be lazy to search.)