I actually have a working'ish prototype of this project laying on my table right now.
It's a 120mm noctua fan being controlled by pwm i relation to the temperature. It also has an oled screen to show temp and fan speed. All controlled trough home assistant via esphome.
I say working'ish because the temp sensor i'm using (dht11) is unreliable and is messing up half the time, so i'm looking into buying a DS18B20 instead.
I'd be happy to share schematics and code if you'd like it.