Installing High Sierra on Mac mini 2018 for Photoshop CS5

According to the info in the Mactracker app, available in the App Store, the oldest macOS version that will run on the 2018 Mac mini is MacOS 10.14 Mojave. So, no. There is no installing High Sierra 10.13 on that Mac.

Nope sorry!

The 2018 Mac mini originally shipped with 10.14 Mojave and can not run High Sierra.

Plus going back in versions requires a full erase and reinstall.

You'd have to first install the free version of VMware on the mini, then you could install High Sierra and CS5 within that.

Major problem, though. Adobe not only shut down the activation servers for CS6 and older years ago, but starting about one year ago they no longer help anyone over the phone to manually activate these titles. Doesn't matter if you have proof of purchase and a valid serial number. They won't do it.

No. Its minimum OS version is Mojave.

(263980)

These days, Photoshop is subscription (rental) only.

There used to be a $10/month Photography Plan that included access to Lightroom (cloud version), Lightroom Classic, and Photoshop. But Adobe no longer offers it to new subscribers. You now have to spend $20/month, which gets you the stuff that was in the $10/month plan, plus the use of 1 TB of Adobe cloud storage.

Adobe – Adobe Photography Plan – Compare Plans

Even Photoshop Elements now is a pseudo-rental program. The current version has a "3-year-license" which means that it will stop working 3 years after you start using it – even if it is otherwise still compatible with the version of macOS you are running at that time.

If you do not need Photoshop, per se, there are alternatives, such as

• Affinity Studio – basic version will run on Catalina and up, and is "free with registration". (Unlocking the AI features would require a paid subscription and an Apple Silicon Mac, which the 2018 Mac mini isn't.)
• The GNU Image Processing Program (GIMP)
• A couple of other Open Source programs for working with Raw images – marketable and rawtherapee.

However, there may be a learning curve (sometimes a steep one) involved with switching to these programs.

You're welcome.

❝Planning is priceless. Plans are worthless.❞ 😉

Servant of Cats wrote:

working with Raw images – marketable and rawtherapee.

The spell checker got you on this one. It should be Darktable and not marketable.