Hide the download buttons in browers supporting the controlList attribute.

hide-download-buttons-for-embeds.php

<?php
/**
 * Hide Download Buttons for Embeds
 *
 * @package hdboe
 * @author  Bernhard Kau
 * @license GPLv3
 *
 * @wordpress-plugin
 * Plugin Name: Hide Download Buttons for Embeds
 * Plugin URI: https://gist.github.com/2ndkauboy/f9b357002202c06aeeca9431f6772dc4
 * Description: Hide the download buttons in browers supporting the controlList attribute.
 * Version: 1.0.0
 * Author: Bernhard Kau
 * Author URI: https://kau-boys.de
 * Text Domain: hide-download-button-on-embeds
 * License: GPLv3
 * License URI: https://www.gnu.org/licenses/gpl-3.0.txt
 */

/**
 * Add the controlsList attribute to audio blocks to hide the download button
 *
 * @param string $block_content The block content about to be appended.
 * @param array  $block         The full block, including name and attributes.
 *
 * @return string
 */
function hide_download_buttons_on_embeds_render_block( $block_content, $block ) {
	if ( 'core/audio' === $block['blockName'] ) {
		$block_content = str_replace( '<audio ', '<audio controlsList="nodownload" ', $block_content );
	}
	if ( 'core/video' === $block['blockName'] ) {
		$block_content = str_replace( '<video ', '<video controlsList="nodownload" ', $block_content );
	}

	return $block_content;
}
add_filter( 'render_block', 'hide_download_buttons_on_embeds_render_block', 10, 2 );