Yeah crazy deal, almost nobody gets the full installer anymore, I think Apple is afraid were to stupid to handle a full installer. :(
No idea if this still works...
The High Sierra instructions...
http://osxdaily.com/2017/09/27/download-complete-macos-high-sierra-installer/
John Lockwood Level 6 (13,119 points)
Aug 21, 2019 8:01 AM in response to ednarcoleptic
In theory you download a full High Sierra installer from the Mac App Store. It is not listed anymore because Apple are encouraging people to use Mojave instead. There is an Apple KB article which however provides a direct link to the (hidden) item on the Mac App Store.
How to upgrade to macOS High Sierra - Apple Support
Scroll down to item 4 in the above document.
Of course as others have pointed out sometimes this results in only getting a 'stub' installer which is not suitable for then creating a bootable USB drive installer.
The way that I have found that is consistently able to download full installers is to run installinstallmacos.py as per
https://github.com/munki/macadmin-scripts
Ideally you run this on the Mac model you want to install on to.