If you want to create a send-only endpoint, a ServiceBusTriggeredEndpointConfiguration doesn't make any sense, as there won't be a queue.
But setting up a send-only NServiceBus endpoint using NServiceBus.Extensions.DependencyInjection won't work either, because the .UseNServiceBus(…) extension method doesn't support IFunctionsHostBuilder.
I think this also affects the Worker hosting model as IFunctionsHostBuilder is located in Microsoft.Azure.Functions.Extensions.DependencyInjection.