Structuremap - dependency injection - EF Core DBContext lifetime per request

Has anyone had any luck setting up an EF Core DBContext with Structuremap "correctly" (what is correctly?)

DBContext needs to be a singleton across the lifetime of the request.

I understand that the default lifecycle is Transient. I understand that that will get a nested container, which effectively means "per request" when running under web api / mvc? (see this)

But, looking at this code, isn't the dbcontext going to be an Application Lifetime singleton?

public class DistributedTaskRegistry : Registry
{
    public DistributedTaskRegistry()
    {
        For<DistributedTaskDbContext>().Use(() => new DistributedTaskDbContextFactory().CreateDbContext(null));
        For<IDistributedTaskRepository>().Use<DistributedTaskRepository>();
    }
}

NB this is a "legacy" .Net Framework 4.7 Web Api using EF Core

Edit What happened to HttpContextScoped?