Add a menu conditionally to a specific wordpress custom post type only

add-nav-to-cpt-only.php

//  Adding a menu conditionally only to a CPT to be centered below the header (for now)
//
//  https://codex.wordpress.org/Function_Reference/is_post_type_archive
//
//  https://www.wpbeginner.com/wp-themes/how-to-add-custom-navigation-menus-in-wordpress-3-0-themes/

 
function j66_menu_output_cpt_ambassador() {

	$menu_cpt_ambassador .= wp_nav_menu( array(
		'menu' => 'CPT Ambassador Menu', // Do not fall back to first non-empty menu.  Was Primary Menu
		'theme_location' => 'cpt-ambassador-menu',
		'fallback_cb' => '__return_false'             // Do not fall back to wp_page_menu()
		) 
	);
	$menu_cpt_ambassador .= '</div>';

return $menu_cpt_ambassador;
}


if ( is_post_type_archive( 'ambassadors' ) ) {
	add_action( 'generate_after_header', 'j66_menu_output_cpt_ambassador' );
}


function j66_cpt_ambassador_menu() {
  register_nav_menu('cpt-ambassador-menu',__( 'CPT Ambassador Menu' ));
}
add_action( 'init', 'j66_cpt_ambassador_menu' );