NET 5.0 web project - unable to change connection URL at startup (+ Docker)

I think I pretty much tried every possible way but no matter what I do, my NET 5.0 web app always connects to localhost:5000.

At startup I get this:

webbackend     | warn: Microsoft.AspNetCore.Server.Kestrel[0]
webbackend     |       Unable to bind to http://localhost:5000 on the IPv6 loopback interface: 'Cannot assign requested address'.
webbackend     | info: Microsoft.Hosting.Lifetime[0]
webbackend     |       Now listening on: http://localhost:5000
webbackend     | info: Microsoft.Hosting.Lifetime[0]
webbackend     |       Application started. Press Ctrl+C to shut down.
webbackend     | info: Microsoft.Hosting.Lifetime[0]
webbackend     |       Hosting environment: Production
webbackend     | info: Microsoft.Hosting.Lifetime[0]
webbackend     |       Content root path: /app

Even though I have these in place:

Program.cs:

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureLogging(logging =>
        {
            logging.ClearProviders();
            logging.AddConsole();
        })
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.UseKestrel()
                      .UseStartup<Startup>()
                      .UseUrls(http://0.0.0.0:80);
        });

appsettings.json:

  "commands": {
    "web": "Microsoft.AspNet.Server.Kestrel --server.urls http://0.0.0.0:80"
  }

Dockerfile:

ENTRYPOINT ["dotnet", "webbackend.dll", "--urls", "http://0.0.0.0:80"]

docker-compose.yml:

webbackend:
    image: local_webbackend
    container_name: webbackend
    networks:
        - my_network
    environment:
        ASPNETCORE_URLS: http://+:80
    ports:
        - "5001:80"
    expose:
        - "5432"
        - "5001"
    depends_on:
        postgresdb:
            condition: service_healthy

I really don't understand what is going on.

I just want this app to connect to localhost:80 inside its docker container. This port should then be connected to 5001 in the docker-compose network.