Today I added the Sonof TH Elite smart temperature humidity controller to my freezer

Behind the top drawer is the original temperature sensor

Behind the middle drawer was an unused position for a temperature sensor. 

And so I drilled a hole through the back of the freezer and mounted the DS1820 temperaure sensor. 

The cable simply comes out of the back side, behind the heat radiator. 

And the sonoff I screwed on the insulation material. It still doesnt control anything, it just measures the temperature.