how to pull images with no add_theme_support('post_thumbnails')

I am developing a portfolio page for my site and I gotten as far as the functionality where as I hover over a listed name of each project it will display the same title on the left hand side of the site like this:

enter image description here

What I would like to do is for when you hover over the title of project on the right hand side, an image from the media library appears on the left hand side, just so I can start making some progress. Unfortunately, this WordPress build is different, I did not build it from scratch and I noticed in the functions.php page, there is no add_theme_support(‘post_thumbnails’), instead this is all I see in functions.php:

<?php
/**
 * Theme functions and definitions.
 *
 * Sets up the theme and provides some helper functions
 *
 * When using a child theme (see http://codex.wordpress.org/Theme_Development
 * and http://codex.wordpress.org/Child_Themes), you can override certain
 * functions (those wrapped in a function_exists() call) by defining them first
 * in your child theme's functions.php file. The child theme's functions.php
 * file is included before the parent theme's file, so the child theme
 * functions would be used.
 *
 *
 * For more information on hooks, actions, and filters,
 * see http://codex.wordpress.org/Plugin_API
 *
 * @package   CMMS
 * @author    Creative MMS
 * 
 * 
 * @since     1.1.0
 */

/*---------------------------------------------------------------------------*/
/*  Load the parent style.css file
/*---------------------------------------------------------------------------*/

add_action('wp_enqueue_scripts', 'enqueue_parent_styles');
function enqueue_parent_styles() {
    wp_enqueue_style('parent-style', get_template_directory_uri().'/style.css');
}

/*------------------------------------------------------------------
[Load Files]
-------------------------------------------------------------------*/
function cmms_child_load_files() {

    $dir = get_stylesheet_directory();

    // Include ACF Theme Functions
    require_once ( $dir.'/inc/acf/acf_groups.php' );
    require_once ( $dir.'/inc/acf/acf.php' );
}

add_action('acf/init', 'cmms_child_load_files');

/*------------------------------------------------------------------
[Add Child scripts]
-------------------------------------------------------------------*/
function cmms_child_assets() {

    // Directory to pull assets from
    $dir = get_stylesheet_directory_uri();

    //Use for DEV
    //wp_enqueue_script('child-scripts', $dir.'/assets/js/child-scripts.js', array('jquery'), '1.0', true);
  wp_enqueue_script( 'cmms-tween-max', $dir . '/assets/js/plugins/ScrollMagic/TweenMax.min.js', array( 'jquery' ), '1.0', true );
  wp_enqueue_script( 'cmms-scroll-magic', $dir . '/assets/js/plugins/ScrollMagic/ScrollMagic.min.js', array( 'jquery' ), '1.0', true );
  wp_enqueue_script( 'cmms-animation', $dir . '/assets/js/plugins/ScrollMagic/animation.gsap.min.js', array( 'jquery' ), '1.0', true );
  wp_enqueue_script( 'cmms-add-indicators', $dir . '/assets/js/plugins/ScrollMagic/debug.addIndicators.min.js', array( 'jquery' ), '1.0', true );

    //Use for PRODUCTION
     wp_enqueue_script( 'cmms-child-app', $dir . '/assets/js/cmms-child-app.min.js', array( 'jquery' ), '1.0', true );

}
add_action('wp_enqueue_scripts', 'cmms_child_assets');

How do I load some images from my media library, without add_theme_support(‘post_thumbnails’) in functions.php? That is the only way I know how to do it. The idea being that then I add this piece of code:

<?php the_post_thumbnail(); ?>

here:

<li class="item <?php if ($count == 1) : ?>active<?php endif; ?>" id="<?= $count; ?>"><?php the_post_thumbnail(); ?></li>

The above code is from archive-work.php:

<?php
/**
 * Work template file.
 *
 * This is the most generic template file in a WordPress theme and one of the
 * two required files for a theme (the other being style.css).
 * It is used to display a page when nothing more specific matches a query.
 * For example, it puts together the home page when no home.php file exists.
 *
 * Learn more: http://codex.wordpress.org/Template_Hierarchy
 *
 * @package   CMMS
 * @author    Creative MMS
* 
 * 
 * @since     1.0.0
 */

get_header(); ?>


    <div class="cmms-house">

        <div class="content-area cmms-clr">

            <main class="site-main cmms-clr">

                <?php
                // Display page header
                //get_template_part( 'partials/archives/header' ); ?>

                <?php
                // Check if posts exist
                if ( have_posts() ) : ?>

                    <div class="work-entry cmms-clr">   
                        <div class="work-col work-left">
                            <ul>
                            <?php
                                // Get query
                                global $wp_query;

                                // Count
                                $count = 1;

                                // Loop through posts
                                while ( have_posts() ) : the_post(); ?>

                                    <li class="item <?php if ($count == 1) : ?>active<?php endif; ?>" id="<?= $count; ?>"><?php the_post_thumbnail(); ?><?= get_the_title(); ?></li>

                            <?php
                                // End loop
                                $count++; endwhile;
                            ?>
                            <?php wp_reset_postdata(); ?>
                            </ul>
                        </div><!-- .left -->

                        <div class="work-col work-right">
                            <ul>
                            <?php
                                // Get query
                                global $wp_query;

                                //Counter
                                $counter = 1;

                                // Loop through posts
                                while ( have_posts() ) : the_post(); ?>

                                    <li class="list-right" data-trigger="#<?= $counter; ?>"><?= get_the_title(); ?></li>

                            <?php
                                // End loop
                                $counter++; endwhile;
                            ?>
                            <?php wp_reset_postdata(); ?>
                            </ul>
                        </div><!-- .right -->

                    </div><!-- .work-entry -->  

                    <?php
                    // Include pagination template part
                    cmms_include_template( 'partials/global/pagination.php' ); ?>

                <?php
                // Display no posts found message
                else : ?>

                    <?php get_template_part( 'partials/entry/none' ); ?>

                <?php endif; ?>

            </main><!-- .main -->

        </div><!-- .content-area -->

<?php get_sidebar(); ?>

<?php get_footer(); ?>

Solutions Collecting From Web of "how to pull images with no add_theme_support('post_thumbnails')"

If you don’t want to modify the theme or add a child theme to handle post thumbnail support, you can do it via a plugin by attaching a callback to the after_setup_theme hook:

<?php
/*
Plugin Name: WPSE Post Thumbnail Support
Plugin URI: 
Description: Adds post thumbnail support to theme.
Version: 0.0.1
Author:
Author URI:
License: GPL2/Creative Commons
*/


add_action( 'after_setup_theme', 'wpse_theme_setup' );
function wpse_theme_setup() {
    /*
     * Enable support for Post Thumbnails on posts and pages.
     */
    add_theme_support( 'post-thumbnails' );
}

Alternatively, you could create your own attachment image upload functionality (personally, I use CMB2 for this) then grab the image by the meta ID and pass it to wp_get_attachment_image().