Turn Astra Secondary Menu into LiteSpeed ESI Block

functions.php

<?php

add_filter( 'wp_nav_menu', function( $nav_menu_html, $args ) {
	if ( $args->menu_id == "ast-hf-menu-2" ) {
		if ( apply_filters( 'litespeed_esi_status', false ) )
			return apply_filters( 'litespeed_esi_url', 'astra_secondary_menu', 'Secondary Menu', array( 'nav_menu_html' => $nav_menu_html, 'args' => $args ), $control = 'private,no-vary', $silence = false );
	}
	return $nav_menu_html;
}, 10, 2);

add_action( 'litespeed_esi_load-astra_secondary_menu', function ( $atts ) {
	echo $atts['nav_menu_html'];
});