Now the Country Tag Helper supports .NET Standard 2.0 . This means that support .NET Core 2.0 .
Also, I have made a NuGET package in order to install on every .NET Core 2.0 application with explanations: https://www.nuget.org/packages/CountryTagHelper
The only trouble here was to add references and make documentation in VS2017 about package ( see https://docs.microsoft.com/en-us/nuget/guides/create-net-standard-packages-vs2017 )
As I said , the source is at GitHub https://github.com/ignatandrei/CountryTagHelper and demo at http://countrytaghelper.apphb.com/
What remains to be done:
add select2 with image flags
provider / dependency injection for FromIP
readme.md / wiki on github