I want to connect a wired device to my network only and not extend the WIFI network.
-Not adding an extra SSID
-Not hiding the SSID to overcome the problem of not being able to disable the Extended Network

-Just connect an device via Ethernet port and connect it wireless to the existing WIFI network (TP-Link deco M5)

Now in the Tether app (iphone) you can click 'tools' > 'Extended Network' and there is a Wireless slider button indicating that you can switch off the Extended Wireless Network.
 

However when I switch this to off I get the error message 'Keep at least one wireless network enabled to use this app.'

We still would have the main WIFI network to which the adapter is also connected. So that would be the 'at least one wireless network' I do not understand why I cannot switch off the Extended Network. What is the use of the switch?

Please confirm if I can disable (not hide) the Extended Network to just connect a wired device to a wireless network. If this is not possible I'm afraid I have to return this product and select a product / vendor which does allow this. I you have another Extender that would allow the switch off of the Extended Network please do let me know.

Thanks in advance