Hello Bero ,

As you want to broadcast only 2.4GHz on your devices, yes its possible to do the same.

Kindly login to the web manager page : 10.0.0.1 with user name :admin and password: password (if not customized)

After logging in to Arris surfboard select Wi-Fi towards right side of the page choose 5GHZ click on Edit and on Wireless Network click on Disable option

As we had disabled 5GHz,now only 2.4GHz will be available to broadcast .

Hope this information helps.