This seems to work:
kirby()->routes([
[
'pattern' => '(:any)',
'action' => function($uid) {
$page = page($uid);
if(!$page) $page = page('database/' . $uid);
if(!$page) $page = site()->errorPage();
return site()->visit($page);
},
'filter' => function($route) {
if(in_array('sitemap.xml', $route->arguments())) { return false; }
},
]
]);