Package 'Microsoft.AspNet.SignalR.Core 2.2.2' was restored using '.NETFramework,Version=v4.6.1'

That's not the Core version of SignalR, that's the core package of the "classic" version.

SignalR was rewritten from scrach for .NET Core. The first alpha version was released on September 2017 as Microsoft.AspNetCore.SignalR. The latest version is 1.0.0 Alpha 2, released on October.

As the blog post explains, this is a significant redesign. You'll have to experiment with the new SignalR to see how the changes affect your application

You should probably track the Github repository and check this video that explains why SignalR was redesigned

I was having the same problem, I solved installing Microsoft.EntityFrameworkCore before Microsoft.AspNetCore.Identity

PM> Install-Package Microsoft.EntityFrameworkCore -Version 2.2.2

PM> Install-Package Microsoft.AspNetCore.Identity -Version 2.2.0

You can omit -Version to get latest stable version of the Package.