Currently `ECSOperator` propagates `platform_version` parameter either in case `launch_type` is `FARGATE` or there is `capacity_provider_strategy` parameter provided. The case with `capacity_provider_strategy` is wrong. Capacity provider strategy can contain a reference on EC2 capacity provider. If it's an EC2 capacity provider, then `platform_version` should not be propagated to the `boto3` api call. And it's not possible to do so with the current logic of `ECSOperator` because `platform_version` is always propagated in such case and `boto3` doesn't accept `platform_version` as `None`. So in order to fix that `platform_version` should be an independent parameter and propagated only when it's specified, regardless which `launch_type` or `capacity_provider_strategy` is specified. That should also simplify the logic of `ECSOperator`.

I will prepare a PR to fix that.
tests/providers/amazon/aws/operators/test_ecs.py
wait_mock.assert_called_once_with()
        check_mock.assert_called_once_with()
        xcom_del_mock.assert_called_once()
        assert self.ecs.arn == 'arn:aws:ecs:us-east-1:012345678910:task/d8c67b3c-ac87-4ffe-a847-4785bc3a8b55'
    @parameterized.expand(
        [
            ['EC2', None],
            ['FARGATE', None],
            ['EC2', {'testTagKey': 'testTagValue'}],
            ['', {'testTagKey': 'testTagValue'}],
        ]
    )
    @mock.patch.object(ECSOperator, '_xcom_del')
    @mock.patch.object(ECSOperator, '_xcom_set')
    @mock.patch.object(ECSOperator, '_try_reattach_task')
    @mock.patch.object(ECSOperator, '_wait_for_task_ended')
    @mock.patch.object(ECSOperator, '_check_success_task')
    def test_reattach_save_task_arn_xcom(
        self, launch_type, tags, check_mock, wait_mock, reattach_mock, xcom_set_mock, xcom_del_mock
    ):
        self.set_up_operator(launch_type=launch_type, tags=tags)  
        client_mock = self.aws_hook_mock.return_value.get_conn.return_value
        client_mock.describe_task_definition.return_value = {'taskDefinition': {'family': 'f'}}
        client_mock.list_tasks.return_value = {'taskArns': []}
        client_mock.run_task.return_value = RESPONSE_WITHOUT_FAILURES
        self.ecs.reattach = True
        self.ecs.execute(self.mock_context)
        self.aws_hook_mock.return_value.get_conn.assert_called_once()
        extend_args = {}
        if launch_type: