Yes, I did finally find a solution. In the Google Home app, open the
thermostat in question. Tap Settings (gear icon) and then schedules.
From the drop down below the word schedules, choose fan instead of
temperature. You can then set the fan to run ...
I also have this problem. I just got a brand new Nest thermostat and I
want the fan to run continuously to keep the air moving in our house,
there is no option to do so. Did anyone ever find a solution or work
around for this?