To test my idea of controlling the power to the fan via the MOSFET, I wired up a fan on the breadboard to be controlled by the MOSFET, similar to how I wired up the LED to blink for an earlier project log. (It's a Noctua NF-B9 redux-1600 PWM. For this test, it doesn't have a PWM input and so it runs at full speed.) I kept the LED (with a source voltage coming from the 3.3v output of the ESP32) as a visual reference. I changed the on/off interval from half a second to 5 seconds to give the fan time to come up to speed. The fan is powered by a 12v input (as is the ESP32, come to think of it).