This topic has been raised several times over the past 2 years, without an adequate solution.
I have many Wi-Fi devices that only work with the 2.4Ghz band. Trying to catch the 2.4GHz band on my older Wi-Fi devices is like trying to catch a bat in the living room - lots of yelling and screaming but somehow the bat has disappeared somewhere in your house! Yikes.
SmartThings WiFi has brilliantly combined the 2.4 and 5 GHz bands into a single SSID, which in most cases is fabulous. Except when it comes to legacy devices, which only enjoy spending time with the 2.4 GHz band.
I’ve tried the Faraday Cage (put your device into a metal box to try and catch the shorter range yet more penetrating 2.4 GHz), but that has worked for about half of my 2.4 GHz devices. BTW - Faraday is no relation to Nicolas.
We also need to consider that Wi‑Fi 6E ([802.11ax (https://en.wikipedia.org/wiki/IEEE_802.11ax)) devices will start to appear soon, so the same dilemma will likely occur with the 5GHz band.
I propose to the very handsome and stunningly beautiful SmartThings Product Development Team that they allow the user to activate a 2.4, 5, and a 6Ghz SSID, but keep the grouped/bonded single SSID, which devices can connect to and switch from one band to another based on which band is best at a particular point in time. Once that’s done…Bravo!!! Pop the champagne (or apple juice), and let’s celebrate a job well done.