Could be the thermostat is stuck or the ECTS is not working. The ECM is not reading any valid temperature.
The fan keep running after switching off is a safety measure when the ECM cannot read the temperature it will keep the fan blowing for 10 to 15 mins after you switch off to make sure the car is not in a situation where it can cause a fire (as the ECM cannot determine if the engine is ice cold or burning hot).
Once you fix the temperature reading issue ...the fan issue will go away too.
2018 equinox 1.6l Diesel LT, Hecho en Mexico, julio 2017