Generated routes are now incorrect as a result of
https://github.com/phpbb/phpbb/pull/2921 / https://tracker.phpbb.com/browse/PHPBB3-13036

For example, a route for a front end controller page, generated on a page in the ACP (such as in the extensions ACP modules) has /adm/ in its URL...

The url should be (used to be): http://localhost/phpbb/page
But is instead this: http://localhost/phpbb/adm/page