Popup critical css generation by force

functions.php

/**
 * Add popup/library content to Divi 5 dynamic CSS detection.
 *
 * This allows Divi to detect modules used inside popup CPT layouts
 * so their CSS is included in the dynamic CSS file (et-divi-dynamic.css).
 *
 * @param string $content Content string used by Divi to detect modules.
 * @return string Modified content with popup layouts appended.
 */
function df_add_popup_content_to_dynamic_css_detection( $content ) {
	// Only run on frontend and when Divi 5 dynamic assets system exists
	if ( is_admin() || ! class_exists( 'ET\Builder\FrontEnd\Assets\DynamicAssets' ) ) {
		return $content;
	}

	static $popup_content_cache = null;

	// Use cached content if already built
	if ( null !== $popup_content_cache ) {
		return $content . ' ' . $popup_content_cache;
	}

	$popup_posts = get_posts( [
		'post_type'      => 'difl_popup',
		'posts_per_page' => -1,
		'post_status'    => 'publish',
		'fields'         => 'ids', // performance optimization
	] );

	if ( empty( $popup_posts ) ) {
		return $content;
	}

	$popup_contents = [];

	foreach ( $popup_posts as $post_id ) {

		$post_content = get_post_field( 'post_content', $post_id );

		if ( ! empty( $post_content ) ) {
			$popup_contents[] = $post_content;
		}
	}

	if ( ! empty( $popup_contents ) ) {
		$popup_content_cache = implode( ' ', $popup_contents );
		$content            .= ' ' . $popup_content_cache;
	}

	error_log($content);

	return $content;
}

add_filter(
	'divi_frontend_assets_dynamic_assets_content',
	'df_add_popup_content_to_dynamic_css_detection',
	10,
	1
);