Localhost not found after migrating application from .net 5 to .net 6

I am unable to run my web application project in IIS Express after migrating from .net 5 to .net 6. I get an error stating that "the localhost page can't be found."

From what I've been able to learn, I have gone through the proper steps to migrate between target frameworks. I have changed the target framework to .net 6 in application properties, and I have updated all affected NuGet packages using the NuGet Pkg Manager. No errors are shown when I build the project, and I have ensured Visual Studio is updated to the latest version, 17.2.5 as of this writing.

The IIS Settings in my launchsettings.json file are as follows:

  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:35317",
      "sslPort": 44352
    }
  }

and I do have an Index view return in my home controller. Yet I still get the error that

No webpage was found for the web address: https://localhost:44352/

when I run the application.

I am retaining the "old" hosting model of Startup.cs and Program.cs from the .Net 5 build to save time, as I understand per Microsoft that this is acceptable. No changes have been made to the code in either of those files.

What am I missing?

EDIT: My Program.cs code is below, by request of @adrianMoskal

    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });
    }

EDIT 2:

Per @adrianMoskal, I updated my Program.cs file to .NET 6 standard. It now looks like this:

var builder = WebApplication.CreateBuilder(args);

// Add DB Contexts and Services here

// Add services to the container.
builder.Services.AddControllersWithViews();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Home/Error");
    // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
    app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();

app.UseRouting();

app.UseAuthorization();

app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}");

app.Run();

Unfortunately, the error persists.

The answer appears to be "screw you, start over."

I've tried copying my project code to a new .net 6 project -- that is, copying all the views, controllers, and whatnot to the new project and updating the new Program.cs file accordingly -- and I still got the same error. I then tried converting a different .net 5 project to .net 6, and got the same error again. So apparently, converting just doesn't work.

So be it. I quit. I've got too much else to do to worry about this. Thanks to those who responded to this post for trying to help resolve it, anyway.