Note the resistor R4 provides hysteresis -- after the P-channel MOSFET activates it acts to keep the N-channel MOSFET active unless the voltage drops below some level set by R2, R3, R4, and the turn on voltage of Q1. You just need to tune them appropriate for your components, and granted of course it adds some amount a bit to your BOM cost. But if you need it you need it.
So basically, R2/R3/Q1 set your turn on voltage (experimentally determined or maybe with Spice) and R4 sets your turn off voltage with R2/R3/Q1. The MCU probably uses under 500mA so these parts are pretty cheap... the capacitor is about 5 cents (https://www.digikey.com/product-detail/en/kemet/ESK477M6R3AE...) and the MOSFETs that looks appropriate are in the 6 cent each range.