On the home screen of the surfboard central app under network setting you can see the following option

Main networks

Guest networks

Extended wifi settings

Select Extended wifi setting to disable the band steering option then 

select Main network and there you can see Band steering option again disable that too then you can see both 2.4 and 5G network on the app.

I tried this and am not seeing separate networks. I’m trying to install a smart light bulb and I cannot get it nor my phone to connect to 2.4ghz.

Could you let us know the product model number to assist you further?

I’ve got an S33 modem, W21 main router, and 2 W21s as satellites.

Thank you for the reply!

When you initially set up the MAx W21 main router, you would have created a Wi-Fi name and password, with a single SSID combining both the 2.4GHz and 5GHz bands. 

But unfortunately the MAx W21 do not have an option to separate the bands, but the devices have capability to choose the appropriate Wi-Fi band when connecting.