Use a different template file for front end and submission view

I have defined a custom template file referenced via #theme for my custom webform element.

public function getInfo() {
  $class = get_class($this);
  return [
    '#input' => TRUE,
    '#process' => [
      [$class, 'processWebformElementSeatbooking'],
      [$class, 'processAjaxForm'],
    ],
    '#element_validate' => [
      [$class, 'validateWebformSeatbookingElement'],
    ],
    '#pre_render' => [
      [$class, 'preRenderWebformSeatbookingElement'],
    ],
    '#theme' => 'input__my_webform_seatbooking_element',
    '#theme_wrappers' => ['form_element'],
  ];
}

This input__my_webform_seatbooking_element is rendered fine in the front end, but I get an error when it is rendered in the back end when looking at a submission cause the icons used in the custom front end theme are missing.

Twig\Error\LoaderError: Template "core/themes/seven/assets/icons/icon_minus.svg" is not defined. in Twig\Loader\ChainLoader->getSourceContext() (line 30 of themes/custom/radix_standard/templates/form/input--number.html.twig).

The template file includes a custom input--number.twig template which contains a reference to two SVG files.

<div class="col-12 col-md-6">
  {% include '@hw_radix_standard/form/input--number.html.twig' with {
    attributes: attributes.addClass('form-number')
      .setAttribute('step', element['#step'])
      .setAttribute('min', element['#min'])
      .setAttribute('max', element['#max'])
      .setAttribute('max', element['#max'])
      .setAttribute('oninput', "this.value = this.value.replace(/[^0-9]+/g, '');"),
  } %}
</div>

I am using a customized radix-theme in the frontend and default seven-theme in the backend.
I would like to render it as plain input field in the backend.
If I put '#theme' => 'input__number', I get the plain input field in the back end, but I need a way to use my custom template file in the front end.
I am stuck here. I checked other render elements and webform code.

How is this normally designed to work?
Maybe I am doing it the wrong way round?
Do I have to put a simple twig inside my custom element module and put the fully featured in the radix?

Last thougt was correct. Put a simplified version of input--my-webform-seatbooking-element.html.twig inside the module and the full featured version in the frontend.