Linksys wrt1900ac v2 wireless radio 2.4ghz not showing

Thanks for calling that out. Totally happy to be wrong about that aspect.
I'm out of ideas, though... at this point to me, this seems like a potential hardware failure, especially because the stock firmware didn't fix the issue.

The above picture looks like the wireless section on the PCB

The below picture is the 88w8864 chip

What are these little chips which looks like is working along with the big chip 88w8864?

I can see the pa5522 ic looks a bit fried. Do you see the black burnt spot on the PCB ?