Truly dumb devices are easier to automate than a device with some smarts. For example, take a heater that has a built-in digital thermostat. If you hook it to a smart plug to turn it on and off, when you turn the power back on they usually will not start heating. I have one that you have to use the power switch on the heater face or remote control in order for it to start heating after cycling the power. I could use an IR blaster, but it was just easier to replace the heater with one that when you apply power, it comes on. I have the mechanical thermostat settings all the way up and just control the heat provided by switching it on and off based on the readings from a temperature sensor.
In the case of the server rack, you need to look at what the goal is rather than modifying the device just to be "smart". Does the fan controller do the job it was purchased for? If yes, leave it alone. So what are you wanting the smart portion for? Monitor the temperature in the rack? Use the ST sensor for that with automation to notify you if it gets beyond a certain level. Wanting to shutdown the equipment remotely or completely power on/off? What's the goal?
One thing that I continually think about with my smart home automation: Sometimes making it smarter just makes it more complicated and subject to failure. So I subscribe to the "Two is one, one is none." way of thinking and either have a 2 devices handling the same task for failover (i.e. 2 sirens for security or multiple motion detectors in the same room) or at least have a spare that I can quickly swap out (i.e. spare smartplugs).