IoT manufacturers' devices should handle combined SSIDs, but many don't.
Things to make sure, before trying various workarounds:
• Make sure that the IoT device(s) in question supports the amount and type of characters used in your chosen network name (SSID) and password; some might have limitations here. In general avoid anything but a-z in the network name. I've heard of devices not supporting whitespace in network name (SSID) or password for instance.
• Some IoT devices have alternative set up procedures if the regular way does not work, which could help.
Workarounds that might work:
• Use an old iOS, iPadOS or Android device that only supports 2.4ghz to set up the IoT device.
• Buy a cheap access point or repurpose a wireless router or range extender to broadcast a 2.4ghz only SSID with a different name than your Nest Wifi network name. Connect it by ethernet cable to the primary/ main/ master Nest Wifi puck preferably. Add more ethernet ports by using an unmanaged switch if need be ( https://support.google.com/googlenest/answer/6274262?hl=en ). Make sure this additional Wi-Fi broadcastong device works as an access point only, else you might not be able to connect to the device in question from a device connected yo your Nest Wifi network.
• Walk far enough from the Nest Wifi puck(s) to make sure your phone/ whatever device used for setting up the device in question connects to the 2.4ghz network, then start setting up the device.
• Turn off your Nest Wifi network by removing the power. Feed your laptop (Windows or Mac) an internet connection, either by ethernet cable from your modem, or by mobile network tethering + USB. Then use your laptop to host a 2.4ghz only Wi-Fi with the same network name (SSID) and password as your Nest Wifi network. Get your IoT devices connected to it. Remove the Wi-Fi hosted by your laptop, plug in Nest Wifi, and the IoT devices should jump to the Wi-Fi provided by Nest Wifi.
I don't work for Google.
