How to change Default Controller Type in V9

Questions
1

In Umbraco v9 beta versions there was a way to override the default controller type by issuing:

builder.Services.Replace(new ServiceDescriptor(
            typeof(IUmbracoRenderingDefaults), typeof( MyUmbracoRenderingDefaults ), ServiceLifetime.Singleton));

But the IUmbracoRenderingDefaults interface is gone in rc-001 and I can’t find the correct way to override the default controller type.

Thanks in advance.

This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/106579-how-to-change-default-controller-type-in-v9