The BT Home Hub 6 ( Also known as BT Smart Hub) was what I had and it had the ability to separate the two networks with separate SSIDs. It's not the Smart Hub 2.
I was forced to get the SH2 as the BT Home Hub 6 does not have a phone port for Digital Voice.
Just an idea.
Did they ask for the old hub back? If you have an old one there is nothing to stop you configuring the old one to act as a wireless access point (WAP) and set that to 2.4GHz with a separate SSID. Then you just turn the 2.4GHz off on the Smart Hub 2, leaving that to deal with 5GHz.
They have sent a returns bag for the old router but in My BT it also says a Failure to Return Charge of £0.
I asked if I had to return it in another post and was told that as I have had the old router since before 13th December 2019 I don't have to return it.
Not sure I can be bothered with having 2 routers though but something to consider.
Fair enough. Just for the record, if you decide to try it.
Basically, disable/turn off everything except the Wi-Fi. Particularly the DHCP, (you can’t have two DHCPs in the same network unless you create a split-scope), but you will need to give the old hub a static IP address that doesn’t clash with anything else in your network. Then you connect the two hubs LAN port to LAN port and you’re good to go.