how to Upgrade to 10.15?

[Raven]

My wife has had a Mac Mini since 2011.
The OS is still at 10.13.6. 350GB used of 500GB drive.
Mostly uses it for book keeping, photos, browsing.
It won't let Safari v13.1.2 download some bank statements anymore
If I upgrade it to 10.15, is there anything else to be aware of besides backing up to her External Hard Drive using Super Duper?
Thanks for your advice!

[Xairbusdriver]

a Mac Mini since 2011

So it is a Pre-2012 (older than 2012) model.
You might want to check the hardware requirements for using Catalina macOS 10.15:

• Every Mac dot com
• Here's a site that lists IN-compatible hardware. Just check System Information for your model identifier.
• The "horses mouth".

[Raven]

It tells me the 2011 Mac mini will not upgrade to Catalina or later.
Is the only option then for her to buy a new Mac?

Considering her basic usage, would you suggest a low end iMac or a MacBook Pro with OS12 or 13?
She does a lot of accounting at home and would a 15" screen be the best size?

[Xairbusdriver]

I'm sure whatever new box you buy will have the newest OS at whatever date it was built. Even a refurb will usually have the current OS. You may be able to find a slightly older "open-box" model, it might still have Big Sur (11).

Unless you need the portability of a laptop, a desktop model will be much less expensive. Since you already have a suitable(?) monitor (as well as keyboard/mouse), a new mini would be the least expensive. A new iMac will have a 24" monitor, you might be able to find a 21" model.

Don't forget to ask about any trade-in value!