How to install OS Catalina on a new SSD install

Formatted the SSD as suggested by Allan and I, then startup in macOS Recovery mode using Option-Command-R to install the latest compatible macOS for that year model Mac mini which is Catalina.

see > Use macOS Recovery on an Intel-based Mac - Apple Support

• Option-Command-R: Start up from macOS Recovery over the internet. Use this key combination to reinstall macOS and upgrade to the latest version of macOS that’s compatible with your Mac.

Put the SSD into a USB enclosure or on a USB to SATA adapter and format it APFS/GUID Partition Map.

Then use CarbonCopyCloner or SuperDuper to Clone your Macintosh HDD to the SSD.

After that swap out the HDD with the SSD and away you go.

You handle that BEFORE installing the new drive.

You need to CLONE, not copy, the old drive the the new one before removing the old one from the computer. That is how I transferred everything from the old HDD to an SSD on my 2012 Macbook Pro.

Get an inexpensive USB3 empty drive enclosure like this: https://eshop.macsales.com/item/OWC/ES2.5BU3B/ to be a transfer enclosure. Makes this SO much easier!

I recommend Carbon Copy Cloner (CCC) because it prompts you to recreate the important Recovery partition on the new drive.

Connect the transfer enclosure to the Mini and use Disk Utility to format the SSD. Use CCC to clone the old drive to the new. Once things are transferred and you confirm that the new SSD is bootable in the enclosure, only then do you move the SSD to its new internal home.

doesn't always work!

if cannot use the online recovery reinstall option on some older laptops make sure a few things are in line

1)date on device must be set

2)drive must be properly formatted

3)OS being installed must be newly downloaded (had a 5 year old download that would not work...)

4)skip a USB install drive if you have a way to use a cheap enclosure to treat as an external drive

Oops! Sorry den.thed! Got interrupted by a phone call.

No problem. Glad to see that we're on the same page.