Got to say Pimoroni's Fan Shim [1] works well. It is easy to set up, and they have a python library with a systemd service that can auto start and stop the fan

Got to say Pimoroni's Fan Shim [1] works well. It is easy to set up, and they have a python library with a systemd service that can auto start and stop the fan depending on the CPU temperature. While you can get away without cooling, the CPU will be throttled to pieces. [1] https://shop.pimoroni.com/products/fan-shim https://shop.pimoroni.com/products/fan-shim