Ive been trying (unsuccessfully) to do this for the last few days.
I work for a school which specialises in game development with over 1,000 students logging onto many computers. Having to run the installer for each user seems quite excessive...
You used to be able to place the templates in the following directory which VS would then read in the templates, but unfortunately it appears that VS doesnt do that any more
C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\Common7\IDE\ProjectTemplates\CSharp
Link to MS Article
Weve ended up creating a batch file that runs on login which creates a copy of the templates for each user which is working...but not the cleanest option.
I would be interested to see if anyone else has managed to do it any other way.