I divided my WiFi channels between 2.4Ghz and 5Hhz on the router, as I had some of my "stuff" which could connect to the 5G WiFi and some could ONLY to the 2.4Ghz - mainly an old iPhone and a Google ChromeCast - they wouldn't even "find" the available 5G network. It seemed logical to me but then a tech at my broadband provider found this;