I have a question that really doesn't suit this site, might be better here on chat.
In https://diy.stackexchange.com/questions/266763/motion-sensor-switch-always-on user says their smart switch / sensor thing "doesn't need a neutral, and can use the earth instead"
is that because its such a low power usage device that the leakage to ground is insignificant?
Or its doing something funky with AC and somehow rectifying it to DC internally in such a way a GFI won't notice ?