2 different ways to add rel="noopener noreferrer" to linked images in WordPress. Could be improved with a check for external links so we can also add "external".

add-rel-to-images.php

<?php
/**
 * Plugin Name: Add Rel to Images
 * Description: Add rel="noopener noreferrer" to linked images.
 *
 * @package There is no package.
 */

/**
 * With jQuery.
 */
function my_plugin_inline_script() {
	wp_add_inline_script( 'jquery', 'jQuery( document ).ready( function( $ ) { $(".external").each(function() { $(".external a").attr("rel", "external noopener") }); });' );
}

add_action( 'wp_enqueue_scripts', 'my_plugin_inline_script' );

/**
 * Vanilla JavaScript
 */
wp_register_script( 'set-rel', '', array(), '1.0.0', true );
wp_enqueue_script( 'set-rel' );
wp_add_inline_script( 'set-rel', 'document.querySelectorAll(".external a").forEach((el) => { el.setAttribute("rel", "external noopener"); });' );

Use with class "external", e.g.,

<div class="external"><a href="" target="_blank"><img src="/path/to/img" width="" height="" alt=""></a></div>