How to override slideshow item template file?

Hi hockey2112, contrib theme is not a good place for custom templates. Because it can be removed by composer on the next 'composer update'. You have two options to override templates in drupal:
1. Create custom theme and put template there. You can inherit custom theme from your contrib theme:
https://www.drupal.org/docs/develop/theming-drupal/creating-sub-themes →
2. In file ept_slideshow you can find ept_slideshow_theme_registry_alter() implementation of hook hook_theme_registry_alter(), it allows to define which templates can be overridden in this module. So you can create custom module, for example ept_enhancements:

/**
 * Implements hook_theme_registry_alter().
 */
function ebt_enhancements_theme_registry_alter(&$theme_registry) {
  $ept_module = 'ebt_enhancements';
  $module_path = \Drupal::service('extension.list.module')->getPath($ept_module);
  $base_theme = 'paragraph';
  $theme_registry['paragraph__ept_slideshow_item__default'] = [
    'path' => $module_path . '/templates',
    'template' => 'paragraph--ept-slideshow-item--default',
    'render element' => $theme_registry[$base_theme]['render element'],
    'base hook' => $base_theme,
    'type' => 'module',
    'theme path' => $module_path,
    'preprocess functions' => $theme_registry[$base_theme]['preprocess functions'],
  ];
}

levmyshkin,

Thanks for your help with this!

1. Sorry, I should clarify. I am using a subtheme, so my template file is in /themes/contrib/themename_subtheme/templates/. But it is not taking effect on the front-end.

2. I created a module as you suggested. Here are the files I created, in /modules/custom/ept_enhancements:

ept_enhancements.info.yml
ept_enhancements.module
/templates
paragraph--ept-slideshow-item--default.html.twig

/modules/custom/ept_enhancements/ept_enhancements.info.yml:

name: 'EPT Enhancements'
type: module
description: 'Custom enhancements for EPT module.'
package: Custom
core_version_requirement: ^8 || ^9 || ^10
version: '1.0'

/modules/custom/ept_enhancements/ept_enhancements.module

<?php

/**
 * Implements hook_theme_registry_alter().
 */
function ept_enhancements_theme_registry_alter(&$theme_registry) {
  $ept_module = 'ept_enhancements';
  $module_path = \Drupal::service('extension.list.module')->getPath($ept_module);
  $base_theme = 'paragraph';

  $theme_registry['paragraph__ept_slideshow_item__default'] = [
    'path' => $module_path . '/templates',
    'template' => 'paragraph--ept-slideshow-item--default',
    'render element' => $theme_registry[$base_theme]['render element'],
    'base hook' => $base_theme,
    'type' => 'module',
    'theme path' => $module_path,
    'preprocess functions' => $theme_registry[$base_theme]['preprocess functions'],
  ];
}

/modules/custom/ept_enhancements/templates/paragraph--ept-slideshow-item--default.html.twig

{#
/**
 * @file
 * Default theme implementation to display a paragraph.
 *
 * Available variables:
 * - paragraph: Full paragraph entity.
 *   Only method names starting with "get", "has", or "is" and a few common
 *   methods such as "id", "label", and "bundle" are available. For example:
 *   - paragraph.getCreatedTime() will return the paragraph creation timestamp.
 *   - paragraph.id(): The paragraph ID.
 *   - paragraph.bundle(): The type of the paragraph, for example, "image" or "text".
 *   - paragraph.getOwnerId(): The user ID of the paragraph author.
 *   See Drupal\paragraphs\Entity\Paragraph for a full list of public properties
 *   and methods for the paragraph object.
 * - content: All paragraph items. Use {{ content }} to print them all,
 *   or print a subset such as {{ content.field_example }}. Use
 *   {{ content|without('field_example') }} to temporarily suppress the printing
 *   of a given child element.
 * - attributes: HTML attributes for the containing element.
 *   The attributes.class element may contain one or more of the following
 *   classes:
 *   - paragraphs: The current template type (also known as a "theming hook").
 *   - paragraphs--type-[type]: The current paragraphs type. For example, if the paragraph is an
 *     "Image" it would result in "paragraphs--type--image". Note that the machine
 *     name will often be in a short form of the human readable label.
 *   - paragraphs--view-mode--[view_mode]: The View Mode of the paragraph; for example, a
 *     preview would result in: "paragraphs--view-mode--preview", and
 *     default: "paragraphs--view-mode--default".
 * - view_mode: View mode; for example, "preview" or "full".
 * - logged_in: Flag for authenticated user status. Will be true when the
 *   current user is a logged-in member.
 * - is_admin: Flag for admin user status. Will be true when the current user
 *   is an administrator.
 *
 * @see template_preprocess_paragraph()
 *
 * @ingroup themeable
 */
#}
{%
  set classes = [
  'paragraph',
  'paragraph--type--' ~ paragraph.bundle|clean_class,
  view_mode ? 'paragraph--view-mode--' ~ view_mode|clean_class,
  not paragraph.isPublished() ? 'paragraph--unpublished'
]
%}
{% block paragraph %}
  {% block content %}
    {% if content.field_ept_slideshow_link|render %}
      <a href="{{ content.field_ept_slideshow_link.0['#url'] }}">
        {{ content.field_ept_slideshow_slide }}
      <div class="ept-slideshow-content">
		  {{ content.field_ept_slideshow_title }}
		  {{ content.field_ept_slideshow_text }}
	  </div>
      </a>
    {% else %}
      {{ content }}
    {% endif %}
  {% endblock %}
{% endblock paragraph %}
{{ attach_library('core/drupalSettings') }}
{{ attach_library('ept_slideshow/flexslider') }}
{{ styles|raw }}

And here is the result (attached screenshot). As you can see, the new template file is still not reflecting any changes on the website. I'm not sure if I am just missing something obvious, or what...

I should also say, if I make the changes directly to the template file within the module dir, the changes reflect on the website. However, I know that is not a valid best-practices way to make this change since it will be overwritten when the module is updated.

> I should also say, if I make the changes directly to the template file within the module dir, the changes reflect on the website. However, I know that is not a valid best-practices way to make this change since it will be overwritten when the module is updated.

You can create a patch for this module with your updates for the template:
https://vazcell.com/blog/how-apply-patch-drupal-9-and-drupal-10-composer

I can't see what exactly you want to change in Slideshow item. But I can add {{ content|without() }} for other fields in Slideshow Item paragraph type:

{% block paragraph %}
  {% block content %}
    {% if content.field_ept_slideshow_link|render %}
      <a href="{{ content.field_ept_slideshow_link.0['#url'] }}">
        {{ content.field_ept_slideshow_slide }}
      </a>
      {{ content.field_ept_slideshow_title }}
      {{ content.field_ept_slideshow_text }}
      {{ content|without('field_ept_slideshow_slide', 'field_ept_slideshow_text', 'field_ept_slideshow_title') }}
    {% else %}
      {{ content }}
    {% endif %}
  {% endblock %}
{% endblock paragraph %}

That's strange that template can't be overriden with templates folder in custom theme. I will check if it's side effect using template from module.

Try to enable Twig Debuging comments and see where you can override templates. I switched to the another pet project and won't spend much time on EBT/EPT modules for a while at least in this year.