After a day of extreme frustration I now understand that my Samsung ZFold3 uses channel 149 ONLY for the 5ghz hotspot and CANNOT be changed. (2.4ghz works normally but is not sufficient for my requirement). 

After buying and returning two different extenders today (re200/re315, before I knew what was causing the problem) I would like to know if any of the TP-link extenders can access ch149? Or can any of the routers (that support wireless bridging) access ch149? 

I need to use 5ghz/ch149 to get the speeds some of my devices need to stream 4k and most of my devices can use the 5ghz hotspot absolutely fine but I have a couple of devices that only support 2.4ghz. I really don't want to keep swapping between 2.4&5ghz on my phone. 

Or, can the re315 or re200 be flashed with a firmware from another country that supports ch149?