No need to register controllers into container, DefaultControllerActivator works fine.

src/Umbraco.Web.BackOffice/Extensions/BackOfficeServiceCollectionExtensions.cs

@@ -52,6 +52,9 @@ namespace Umbraco.Extensions
 
             services.TryAddScoped<IIpResolver, AspNetCoreIpResolver>();
 
+            // TODO: MSDI - This needs some work, e.g. additional registrations / not registering as UserManager<BackOfficeIdentityUser>
+            // if we want container validation back on.
+
             services.BuildUmbracoBackOfficeIdentity()
                 .AddDefaultTokenProviders()
                 .AddUserStore<BackOfficeUserStore>()

src/Umbraco.Web.BackOffice/Extensions/CompositionExtensions.cs

@@ -1,7 +1,4 @@
 using Umbraco.Core.Composing;
-using Umbraco.Web.BackOffice.Controllers;
-using Umbraco.Web.Common.Controllers;
-using Umbraco.Web.Common.Install;
 using Umbraco.Web.BackOffice.Trees;
 
 // the namespace here is intentional -  although defined in Umbraco.Web assembly,
@@ -27,26 +24,5 @@ namespace Umbraco.Extensions
             => composition.WithCollectionBuilder<TreeCollectionBuilder>();
 
         #endregion
-
-
-        /// <summary>
-        /// Registers Umbraco backoffice controllers.
-        /// </summary>
-        public static Composition ComposeUmbracoBackOfficeControllers(this Composition composition)
-        {
-            composition.RegisterControllers(new []
-            {
-                typeof(BackOfficeController),
-                typeof(PreviewController),
-                typeof(AuthenticationController),
-                typeof(InstallController),
-                typeof(InstallApiController),
-            });
-
-            var umbracoAuthorizedApiControllers = composition.TypeLoader.GetTypes<UmbracoApiController>();
-            composition.RegisterControllers(umbracoAuthorizedApiControllers);
-
-            return composition;
-        }
     }
 }

src/Umbraco.Web.BackOffice/Runtime/BackOfficeComposer.cs

@@ -51,8 +51,6 @@ namespace Umbraco.Web.BackOffice.Runtime
 
             composition.Services.AddUnique<IIconService, IconService>();
             composition.Services.AddUnique<UnhandledExceptionLoggerMiddleware>();
-
-            composition.ComposeUmbracoBackOfficeControllers();
         }
     }
 }

src/Umbraco.Web.Common/Extensions/CompositionExtensions.cs

@@ -1,21 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Reflection;
-using Microsoft.AspNetCore.Mvc;
-using Microsoft.Extensions.DependencyInjection;
-using Umbraco.Core.Composing;
-using Umbraco.Web.Common.Controllers;
-using Umbraco.Web.Mvc;
-
-namespace Umbraco.Extensions
-{
-    public static class CompositionExtensions
-    {
-        public static void RegisterControllers(this Composition composition, IEnumerable<Type> controllerTypes)
-        {
-            foreach (var controllerType in controllerTypes)
-                composition.Services.AddScoped(controllerType);
-        }
-    }
-}

src/Umbraco.Web.Common/Runtime/AspNetCoreComposer.cs

@@ -80,6 +80,7 @@ namespace Umbraco.Web.Common.Runtime
             //register the install components
             //NOTE: i tried to not have these registered if we weren't installing or upgrading but post install when the site restarts
             //it still needs to use the install controller so we can't do that
+            // TODO: MSDI we can fix that
             composition.ComposeInstaller();
 
             var umbracoApiControllerTypes = composition.TypeLoader.GetUmbracoApiControllers().ToList();

src/Umbraco.Web.UI.NetCore/Program.cs

@@ -21,9 +21,8 @@ namespace Umbraco.Web.UI.NetCore
                     x.ClearProviders();
                 })
                 .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup<Startup>(); })
-                // TODO: MSDI - this should probably be on one day, more so when we can reduce the number
-                // of times we build a ServiceProvider from services collection
-                // right now it's just painful.
+                // TODO: MSDI - this should probably be on one day
+                // First we need to resolve the composition conditional registration issues see #8563
                 .UseDefaultServiceProvider(options => options.ValidateOnBuild = false)
                 .UseUmbraco();
     }

src/Umbraco.Web.Website/Extensions/CompositionExtensions.cs

@@ -1,40 +0,0 @@
-using System.Linq;
-using Umbraco.Core.Composing;
-using Umbraco.Web.Common.Controllers;
-using Umbraco.Web.Mvc;
-using Umbraco.Web.Website.Controllers;
-
-namespace Umbraco.Extensions
-{
-    public static class CompositionExtensions
-    {
-        /// <summary>
-        /// Registers Umbraco website controllers.
-        /// </summary>
-        public static Composition ComposeWebsiteUmbracoControllers(this Composition composition)
-        {
-            composition.RegisterControllers(new []
-            {
-                // typeof(UmbProfileController), //TODO introduce when migrated
-                // typeof(UmbLoginStatusController),//TODO introduce when migrated
-                // typeof(UmbRegisterController),//TODO introduce when migrated
-                // typeof(UmbLoginController),//TODO introduce when migrated
-                typeof(RenderMvcController),
-                typeof(RenderNoContentController),
-
-            });
-
-            var umbracoWebAssembly = typeof(SurfaceController).Assembly;
-
-            // scan and register every PluginController in everything (PluginController is IDiscoverable and IController)
-            var nonUmbracoWebPluginController = composition.TypeLoader.GetTypes<PluginController>().Where(x => x.Assembly != umbracoWebAssembly);
-            composition.RegisterControllers(nonUmbracoWebPluginController);
-
-            // can and register every IRenderMvcController in everything (IRenderMvcController is IDiscoverable)
-            var renderMvcControllers = composition.TypeLoader.GetTypes<IRenderMvcController>().Where(x => x.Assembly != umbracoWebAssembly);
-            composition.RegisterControllers(renderMvcControllers);
-
-            return composition;
-        }
-    }
-}

src/Umbraco.Web.Website/Extensions/UmbracoWebstiteServiceCollectionExtensions.cs

@@ -1,8 +1,4 @@
-using System.Collections.Generic;
-using System.Linq;
-using Microsoft.AspNetCore.Mvc;
-using Microsoft.AspNetCore.Mvc.Controllers;
-using Microsoft.AspNetCore.Mvc.ViewEngines;
+using Microsoft.AspNetCore.Mvc;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
 using Umbraco.Web.Website.ViewEngines;
@@ -13,8 +9,6 @@ namespace Umbraco.Extensions
     {
         public static void AddUmbracoWebsite(this IServiceCollection services)
         {
-            services.AddSingleton<IControllerActivator, ServiceBasedControllerActivator>();
-
             // Set the render & plugin view engines (Super complicated, but this allows us to use the IServiceCollection
             // to inject dependencies into the viewEngines)
             services.AddTransient<IConfigureOptions<MvcViewOptions>, RenderMvcViewOptionsSetup>();
@@ -24,8 +18,6 @@ namespace Umbraco.Extensions
 
             // Wraps all existing view engines in a ProfilerViewEngine
             services.AddTransient<IConfigureOptions<MvcViewOptions>, ProfilingViewEngineWrapperMvcViewOptionsSetup>();
-
         }
-
     }
 }

src/Umbraco.Web.Website/Runtime/WebsiteComposer.cs

@@ -14,11 +14,6 @@ namespace Umbraco.Web.Website.Runtime
         public void Compose(Composition composition)
         {
             composition.Services.AddUnique<NoContentRoutes>();
-
-            composition
-                .ComposeWebsiteUmbracoControllers()
-                //.SetDefaultRenderMvcController<RenderMvcController>()// default controller for template views
-                ;
         }
     }
 }