Is it normal for 2018 Mac Mini to make screetchy noises?
If it's a "screechy" noise as you describe the it's very possible it could be either "capacitor squeal or coil whine."

In the audio recording, the fan itself was generating a good deal of (normal) noise so it was difficult to separate the two.  One way to determine if  it is the fan or not is to remove the back cover and stop the fan with your finger while listening for the noise.  If it goes away, it's the fan, if not, it's the logic board or power supply.

However, given that this is basically a brand new Mac mini, I would take it in for service even if it's just to get the problem logged.