问题是，您注册到同名的控制器（HomeController），而没有定义自定义路由，那么.net不知道选择哪个。
您可以使用Route属性为控制器提供自定义路径请参阅此处的文档：https://learn.microsoft.com/en-us/aspnet/core/mvc/controllers/routing?view=aspnetcore-7.0#attribute-routing-with-http-verb-attributes
因此，您可以将Route属性添加到代码中，如下所示：

namespace CoreDemo.Areas.Admin.Controllers
{
    [Route("admin/[controller]/[action]")]
    public class HomeController : Controller
    {
        public IActionResult Index()
        {
            return ControllerContext.MyDisplayRouteInfo();
        }
    }
}

namespace CoreDemo.Controllers 
{ 
    [Route("[controller]/[action]")]
    public class HomeController : Controller 
    { 
        private readonly ILogger _logger;
    
        public HomeController(ILogger<HomeController> logger)
        {
            _logger = logger;
        }
    
        public IActionResult Index()
        {
            return View();
        }
    
        public IActionResult Privacy()
        {
            return View();
        }
    
        [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
        public IActionResult Error()
        {
            return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
        }
        public IActionResult Test()
        {
            return View();
        }
    }
}