The Fly-E3-Pro has a temperature sensor on the PCB, near the X and Y stepper motor drivers, that can be used to monitor the board temperature.
Use the following line to activate the temperature sensor.
M308 S2 P"boardtemp" Y"thermistor" A"Board Temperature" T100000 B4092
The sensor can be added to the temperature graph by selecting
extra on the heater control panel in DWC.
The sensor can also be used to trigger a fan etc when a certain threshold is met.