ASP.NET Core Identity by default uses string as primary key, using GuIdentity you will have guid as a primary key.

Based in project generated by dotnet new mvc --auth Individual

1. Run:

   dotnet add package Msmaldi.AspNetCore.GuIdentity.EntityFrameworkCore --version 3.0.0

2. Create a file User.cs add like:

   using Msmaldi.AspNetCore.GuIdentity;
   
   namespace GuIdentitySample.Mvc.Models
   {
   	public class User : GuIdentityUser
   	{        
   	}
   }

3. In file ApplicationDbContext.cs add and change:

   using Msmaldi.AspNetCore.GuIdentity.EntityFrameworkCore;

   public class ApplicationDbContext : GuIdentityDbContext<User>

4. In file Startup.cs add and change:

   using Msmaldi.AspNetCore.GuIdentity;

   services.AddDefaultIdentity<User>()
   		.AddEntityFrameworkStores<ApplicationDbContext>();

   or if you need use GuIdentityRole and RoleManager

   services.AddIdentity<User, GuIdentityRole>()
   		.AddEntityFrameworkStores<ApplicationDbContext>()
   		.AddDefaultTokenProviders();

5. In file /Views/Shared/_LoginPartial.cshtml:

   @inject SignInManager<User> SignInManager
   @inject UserManager<User> UserManager

6. Delete app.db:

   rm app.db

7. Delete folder:

   rm -r ./Data/Migrations

8. Run:

   dotnet tool install --global dotnet-ef
   
   dotnet ef migrations add CreateGuIdentityInitialSchema -o ./Data/Migrations
   
   dotnet ef database update
   
   dotnet run