Hide metabox for certain post types (including Yoast SEO)

function hide_metaboxes() {
	// To make the editor cleaner, we hide the following metaboxes for certain post types
	// TODO: Replace 'my_custom_posttype' with your own post type slug
	remove_meta_box( 'wpseo_meta', 'my_custom_posttype', 'normal' );
	remove_meta_box( 'relevanssi_hidebox', 'my_custom_posttype', 'advanced' );
}
add_action( 'add_meta_boxes', 'hide_metaboxes', 1000 );