#concrete5 Switch theme via request path for page not found

app.php

<?php
// Tested on 8.5.2a1
Events::addListener('on_before_render', function ($event) {
    $view = $event->getArgument('view');
    if ($view->getViewPath() == '/page_not_found') {

        $request = \Request::getInstance();

        if ($request->getPath() == '/foo' || $request->matches('/foo/*')) {
            $view->setViewTheme('concrete');
        }
    }
});