To do this you will need to disable SmartSteering. I can't find an article to do this but this should get you to the right place:
You will disable SmartSteering and then assign a different SSID for the 2.4 and 5.0 bands. Then get your device to connect to the appropriate SSID.
Correct, the new hub does not allow smart steering to be turned off. Might the addition of an Access Point better address the issue of 2.4 G connections?