OData, Net5: How to implement $count when controllers return entities of multiple types

I am adding OData to an existing large API in .Net5, where the action methods in each controller return different types (such as OrganizationFull, OrganizationList, etc.)

This is working, except that the responses do not contain OData meta data, such as $count. So when a consumer calls /api/OrganizationList?$count=true, it doesn't get the count.

I understand that to get this meta data, I have to add an EDM model, like so:

// Startup.cs

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers()
                .AddOData(opt => opt.Select().Filter().SetMaxTop(10).AddRouteComponents("odata", GetEdmModel()))

        IEdmModel GetEdmModel()
        {
            var odataBuilder = new ODataConventionModelBuilder();

            odataBuilder.EntitySet<OrganizationFull>(nameof(Organization));
            odataBuilder.EntitySet<OrganizationList>(nameof(Organization)); // throws
            return odataBuilder.GetEdmModel();
        }

Here I specified 2 EntitySets, one for each entity type returned from the OrganizationController.

However, this throws an exception "The entity set 'Organization' was already configured with a different EntityType ('OrganizationFull').". And if I remove the EntitySet for OrganizationList, when I hit the List end point, I get a 404.

How can I get my end points to return the $count meta data, while keeping my API (which returns multiple entity types from one controller)?

Start with Startup.cs, ConfigureServices, and GetEdmModel, then trace the OrganizationController endpoints returning OrganizationFull and OrganizationList. Reproduce the duplicate EntitySet exception and the 404 for the list endpoint; done means establishing a supported configuration that preserves both endpoints and returns $count metadata.