Hi!

When doing call in ConfigureServices:

services.AddExtCore(this.extensionsPath, false, new ExtCore.WebApplication.DefaultAssemblyProvider(services.BuildServiceProvider())

You will get the following warning:
warning ASP0000: Calling 'BuildServiceProvider' from application code results in an additional copy of singleton services being created. Consider alternatives such as dependency injecting services as parameters to 'Configure'.

Is this something you are going to address?
It is not recommended to use BuildServiceProvider inside ConfigureServices but the constructor of DefaultAssemblyProvider expects to get a ServiceProvider.

Regards
Anders