function mytheme_disable_gutenberg( $can_edit, $post_type ) {
$disabled_post_types = array( "website", "customer" );
if ( in_array($post_type, $disabled_post_types ) ) {
return false;
}
return $can_edit;
}
add_filter( 'gutenberg_can_edit_post_type','mytheme_disable_gutenberg', 10, 2 );