As far as i know, Photoshop CS5 won’t install on any macOS after macOS Mojave 10.14 because even though the Photoshop CS5 application itself is 64 bit Intel, included components like the installer are 32 bit that Apple no longer supports on macOS since macOS Catalina 10.15.
The same applies for the rest of the applications included in CS5 Production Premium.
https://support.apple.com/en-us/103076
Unfortunately, since most of the time a Mac won’t accept an install of a macOS older than the OS it shipped with, you won’t be able to install macOS Mojave 10.14 on your Mac mini. Besides i don’t believe there was ever a released to the public version of macOS Mojave 10.14 that would run natively on Apple Silicon processors.
If you didn’t have any activation issues as mentioned by Conrad_C, then a Virtual macOS might work depending on how much free space your Mac’s ssd has, since you would need to install a complete macOS like Mojave or older.
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