@Davidstockle if you don't mind you could only have 2.4ghz switched on for the guest WiFi network and use that network for your smart devices. That works for me.

I am using the E4R Decos. If it’s any help, I disabled 2.4GHz on the main Deco network and use that for my 5GHz devices. I then disabled 5GHz on the Deco guest network and use that for my smart...