@JohnfromCt 

Hello John,  What you want to look for is the IoT Network feature (Open App > More > IoT Network). When setting this network up you can specifiy 2.4GHz only.  This will allow you to isolate these devices.

To be clear the 6GHz is not part of the combined SSID/Network.  This is because 6GHz only support WPA3 and 2.4GHz and 5GHZ support WPA2 or a blend of WPA2/WPA3.  So for the combined SSID its only 2.4 GHZ and 5 GHz.  

Alternatively you can also use the perfered band feature if you do not want to setup a IoT network and have to reconfigure your devices.  To use this feature find one of the devices in question inside the Client List and tap on it.  Tap the Connection Preference option then under Preferred band change it to 2.4 GHz.  Repeat for each device you want to set to 2.4 GHz only and that should solve the concern, without reconfiguring any devices. 

  @JohnfromCt 

That will work too.  You can set the main network to be only 2.4 GHz and then set up an IoT network to be 5 Ghz only.  

the other option instead of having to setup a new network is to use the prefered band feature which keeps everything on a single network but you basically lock the client to a specific band.