I just want to share my recent experience with those that have 2012 Mac Mini's...
About 5 months or so ago, I updated my Mini 2.6 quad core / 16gb / 256 ssd to Catalina. Shortly after that I noticed the fans were running audibly loud when the computer was in idle with no apps running...the worst!! I tried all the software tricks to no avail. I accepted the fact my 2012 Mini was on it's way out and began my quest for a new Mac. The other day I went to insert (for the first time) an SD card into the slot on the Mini. The card didn't mount, and when I took it out of the Mini, a bunch of matted dust came out with it. I did this action a couple more times until the card mounted. I then decided to open up the Mini and see how dirty it was inside. Pretty damn dirty! I grabbed some compressed air and a micro fiber cloth and cleaned her out, the turned her on. ZERO FAN NOISE.
Unreal that I hadn't cleaned this thing out in years! I opened one of my more taxing projects and am blown away at how quiet it is. I tripled checked to make sure than fans are still working, which they most certainly are. Of course, the Mini is much cooler to the touch as well. So if your Mini is gasping for air...give this a shot. Peace and love!