Guys, still having issues with this. I downloaded the latest version today, no sign of the PackageTargetFallback tag in the projects and adding it doesn't appear to fix things.
Changing TargetFrameworks to <TargetFrameworks>net461;netcoreapp1.1</TargetFrameworks> seems to help but gives different errors.
Is it realistic to be able to use with Visual Studio for Mac (now on stable release)?