@PGdude
'Smart Connect' is the 'feature' that the router has to produce a single SSID (using the network name, and you think is the 2.4Ghz SSID) that the Router 'interogates' the device to see how it would like to connect. It is NOT fool-proof I've found. That is the device will indicate it can connect to 5Ghz band but it can not. See https://www.tp-link.com/us/support/faq/2595/ for more details.
So to see both the 2.4Ghz and 5Ghz SSID's, you have to turn off Smart Connect.
That said, using the phone Tether or Deco app, looking at the Client List, you can select a device and then look at the Connection Preference. Usually set to AUTO, but IF the device does connect to 5Ghz and you want it on the 2.4Ghz you can specify that and it will do just that. Just turn off the device and back on and it will use that setting.
Other ways to get a true 2.4Ghz SSID, use the GUEST NETWORK, However, disabling Smart Connect is the best way to do this.