Symfony creating an HTML5 Datalist form element

I've been trying to create a DataList in my Symfony application by following this thread. However, the custom template is never loaded, I just get a textfield and no responses when I attempt to search for strings in the list.

Below is my modified code of the linked thread above:

My src/Form/DataListType class:

namespace App\Form;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\OptionsResolver\OptionsResolver;
use Symfony\Component\Form\Extension\Core\Type\TextType;

class DataListType extends AbstractType
{

    public function getParent()
    {
        // return EntityType::class;
        return TextType::class;
    }

    public function configureOptions(OptionsResolver $resolver): void
    {
        $resolver->setRequired(['choices']);
    }

    public function getName() {
        return 'datalist';
    }
}

templates\form\datalist.html.twig:

{% block datalist_widget %}
    <div class="form-group">
        <input {{ block("widget_attributes") }} list="{{ id }}_list" class="form-control" />
        <datalist id="{{ id }}_list">
            {% for choice in form.vars.choices %}
                <option value="{{ choice.value  }}">{{ choice.label }}</option>
            {% endfor %}
        </datalist>   
    </div>
{% endblock %}

My config/packages/twig.yml

twig:
    default_path: '%kernel.project_dir%/templates'

    form_themes:
        - '@FOSCKEditor/Form/ckeditor_widget.html.twig'
        - 'form/datalist.html.twig'

    globals:
        sourceFiles: '@App\Service\SourceFile'

when@test:
    twig:
        strict_variables: true

The config/services.yml is as follows:

parameters:

services:
    # default configuration for services in *this* file
    _defaults:
        autowire: true      # Automatically injects dependencies in your services.
        autoconfigure: true # Automatically registers your services as commands, event subscribers, etc.

    # makes classes in src/ available to be used as services
    # this creates a service per class whose id is the fully-qualified class name
    App\:
        resource: '../src/'
        exclude:
            - '../src/DependencyInjection/'
            - '../src/Entity/'
            - '../src/Kernel.php'
            - '../src/Tests/'

    # add more service definitions when explicit configuration is needed
    # please note that last definitions always *replace* previous ones
        
    form.datalist_type:
        class: Acme\Form\DataListType
        tags:
            -  { name: form, alias: datalist }

I then add the datalist to the form in a controller by doing the following:

...
$builder->add('test', DataListType::class, [
      'choices'  =>  ['one', 'two', 'three']
]);
...

As I mentioned above, the custom Twig template never loads and I just get a textfield.