Welcome to the WP Router sample page. You can find the code that generates this page in /var/lib/mnethosted/hoststor/env/hosted02/www/darienite-prod/public_html/wp-content/plugins/the-events-calendar-community-events/vendor/wp-router/WP_Router_Sample.class.php
This page helpfully tells you the value of the sample_argument query variable: wp-router-placeholder-page