'No database provider has been configured for this DbContext' on SignInManager.PasswordSignInAsync

If AddDbContext is used, then also ensure that your DbContext type accepts a DbContextOptions object in its constructor and passes it to the base constructor for DbContext.

The error message says your DbContext(LogManagerContext ) needs a constructor which accepts a DbContextOptions. But i couldn't find such a constructor in your DbContext. So adding below constructor probably solves your problem.

    public LogManagerContext(DbContextOptions options) : base(options)
    {
    }

Edit for comment

If you don't register IHttpContextAccessor explicitly, use below code:

services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>(); 

I could resolve it by overriding Configuration in MyContext through adding connection string to the DbContextOptionsBuilder:

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        if (!optionsBuilder.IsConfigured)
        {
            IConfigurationRoot configuration = new ConfigurationBuilder()
               .SetBasePath(Directory.GetCurrentDirectory())
               .AddJsonFile("appsettings.json")
               .Build();
            var connectionString = configuration.GetConnectionString("DbCoreConnectionString");
            optionsBuilder.UseSqlServer(connectionString);
        }
    }

This is the solution i found.

https://github.com/aspnet/EntityFramework.Docs/blob/master/entity-framework/core/miscellaneous/configuring-dbcontext.md

Configure DBContext via AddDbContext

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext<BloggingContext>(options => options.UseSqlite("Data Source=blog.db"));
}

Add new constructor to your DBContext class

public class BloggingContext : DbContext
{
    public BloggingContext(DbContextOptions<BloggingContext> options)
      :base(options)
    { }

    public DbSet<Blog> Blogs { get; set; }
}

Inject context to your controllers

public class MyController
{
    private readonly BloggingContext _context;

    public MyController(BloggingContext context)
    {
      _context = context;
    }

    ...
}