I couldn't join in this conversation from a previous post, so would like to revisit it. I found it frustrating that one of the "experts" claimed to have a lot of 2.4 devices that are working just fine, so it must be somebody else's problem (either the user, the developer, or both). I found that answer somewhat arrogant and non-constructive finger-pointing. A lot of end-users are suffering daily with this inability to separate the 2.4 from 5 ghz and would like a final solution. The end user needs a real solution so that all devices can be used as they were intended. To pretend that problem does not exist is reason enough to switch off to the google wifi router system, and start using something a little more inclusive. Right now, the final solution is to throw the Google wifi into the trash.
There is no setting to do what you're asking, unfortunately. This is a mostly a user to user community, therefore if this is important to you, I’d encourage you to also send this feedback directly to Google. You will not receive a response, unless Google need more details from you, however the team are still reading the feedback.
What I can say is, some smart home devices only use the 2.4 GHz band and will not be available for setup if your phone is on the 5 GHz band. You may be able to tell your Android phone to only connect on the 2.4 GHz band temporarily in your phone's Wi-Fi settings, if you have an Android device that is. Refer to the manufacturer's support information to see if your phone has this feature.
The waves of the 2.4 GHz band can travel a greater distance than those of the 5 GHz band. If your phone does not have the ability to switch Wi-Fi bands, try to move farther away from your router and points until your phone moves to the 2.4 GHz band. Then proceed with setting up your smart home devices.
Unfortunately, it comes down to the fact that in general well manufactured devices don't exhibit this problem. In my experience, this tends to occur with typically cheaper, less standards compliant devices. That's just my observation of course, so your mileage may vary.
I can't believe a home platform company is not willing to make a software update that that would resolve the biggest issue with IOT devices as an industry. It feels like roulette every time I try to connect a device, and not the assured experience I expect purchasing from an industry leader. The solution is not to expect all the thousands of tiny rag tag companies to have better standards compliance, the solution is to give your consumers a real way to connect their devices with ease. Google, please don't deflect the problems, own the solution. I mean, unless you don't have the magic sauce anymore.