Updated Mac Mini Later 2012 to Catalina OS X - Slow for over 2 weeks

Did you review the Report? Etrecheck thinks you have a failing hard drive. Good opportunity to upgrade to an SSD.

As I mentioned, a slow, spinning hard drive is not the best choice for either Mojave or Catalina. Not only do you have a 5400 RPM hard drive, it is failing. Double whammy.

Not only do you have a failing 5400 RPM hard drive, you only have 4GB of RAM. Triple whammy.

If you don't have a backup, you should make one now.

Does you Mini have a slow, spinning hard drive or an SSD? Both Mojave and Catalina really need an SSD.

However, that 3-hour delay isn't expected.

Try running Etrecheck and post the report here. Use Share Report > Copy Report and paste it into the Additional Text area (document icon in toolbar, here).

A safe bet is something from Other World Computing. They have a very good reputation. I bought one of their mid-level models a few years ago. I can't remember the specs, but I used it to Make a Fusion drive with the Mini's HDD.

I also have purchased a SanDisk SSD in a 2010 MacBook Pro. It was very cheap, so I bought it to give it a try. Worked great.

Other than that, I don't have enough experience to recommend much. I always get whatever I think I can afford.

It's an eight-year old Mac, but I would bet it would continue to serve you well with an SSD.