This is still an issue and I think it's a bug in the Android app.
The latest update for Nexus devices (7.0 Nougat) doesn't support forcing wifi into 2.4 Ghz-only mode, making it impossible to set up with a Gen 2 device on an Onhub network using the Nexus 5X, 6P, etc.. When I select my dual band SSID, the app immediately pops up a dialog stating that 5 Ghz networks aren't supported (and then frustratingly doesn't offer a way to close said dialog). I dug an iPhone 5S out of storage and, while connected to my Onhub's 5Ghz band, it was able to set things up no problem.
The Android app, for some reason, only acknowledges the 5 Ghz band, even though Wifi analyzer apps and a sample Android app I wrote run on the same device see both the 2.4 and 5 Ghz bands for my network when querying the Android platform.
This sounds like a small issue but it pretty much ruins the out of box experience for anyone with the above configuration (and likely other phones soon to be released with Nougat). Hopefully there's an easy fix isolated to the Android app.