When I try to install the 10.13 Supplemental Update on my High Sierra install (MacPro 4,1 w/ DosDude1's modified installer tool & patches), I get an error that the software is not supported on my system.
I was hoping to install this update, then the latest Nvidia web driver update from today, to see if it would improve the glitchiness I'm getting with my GTX 660 Ti.
If you downloaded the Supplemental Update from Apple Support rather than through the App Store you need to modify the Distribution file contained in the macOSUpd10.13Supplemental.pkg, see below for details.
Modifying the Supplemental Update for High Sierra.
Download Supplemental Update.
Open Supplemental Update.
Move macOSUpd10.13Supplemental.pkg to desktop.
Open Terminal.
Enter pkgutil --expand ~/Desktop/macOSUpd10.13Supplemental.pkg ~/Desktop/Expanded
Open Expanded folder and then open Distribution file in Text Wrangler
Change Distribution file, change Board iD line 33 to <your Macs boardID> at line 41 remove <your Mac model>
Save As .xml file to the Desktop
In Terminal chmod +x ~/Desktop/distribution.xml
Remove the extension .xml
Move new Distribution file to expanded package replacing the original
In Terminal pkgutil --flatten ~/Desktop/Expanded ~/Desktop/Modified.pkg
Using the .pkg extension is crucial.
The Modified package on your desktop should now allow you to install the latest update