My problem is that my internet speed to Apple's server is very slow, and I have 6 devices running macOS so I like to download security updates or system updates only once for all 6 of my devices.
I checked these folders:
$TMPDIR../C/com.apple.appstore/ aka /var/folders/mp/???/C/com.apple.appstore ~/Library/Caches/storeaccountd ~/Library/Caches/storeassetd ~/Library/Caches/storedownloadd ~/Library/Caches/storeinappd
The package is not in either of these folders...
Also, once the file is downloaded and installed, App Store removes the package immediately it seems. Is there a way to prevent App Store from removing updates?