I believe this should work for you:

appautoscalingTarget = aws.appautoscaling.Target(
        resource_name= "my-target",
        min_capacity= 1,
        max_capacity= 2,
        resource_id= Output.all(service[0].name, ecs_cluster.name).apply(lambda args: f"service/{args[0]}/{args[1]}"),
        scalable_dimension= "ecs:service:DesiredCount",
        service_namespace= "ecs"
    )

Ill try this again. I did do the above.