Have you checked the high limit thermostat and the thermal cut off. They are on the heating can that houses the heating element. If either of those two are burnt out that is your issue.
Another remote possibility is the centrifugal switch on the drive motor. If that has burnt contacts or wiring to the second side of the heating element it to can prevent the dryer from heating.
Finally if all else are good the heater relay on the control board is bad or going bad and yes that would require replacing the electronic control board.

I have never heard of testing the high limit thermostat that way. As a mater of fact if you heat up a high limit thermostat until it no longer show continuity it is basically done. Testing a thermistor that way is correct but a thermostat and high limit cut off are one and done. If you heat up either the high limit thermostat and or the thermal cut off fuse they do not reset and must be replaced.
The high limit thermostat and thermal cut off are numbers 47 and 48 in the picture. These should both be replaced even if only one is bad.
Whirlpool 279973 Thermal Cut Off Kit - AppliancePartsPros.com
The thermistor is part 42 and it is responsible for cycling the heater on and off. It is the one that can be tested by heating it up slightly to see if there is a change in ohms resistance.
Whirlpool WP8577274 Dryer Thermister - AppliancePartsPros.com
The thermal fuse number 59 must be good or the unit wouldn't start at all.