Related post: https://area51.phpbb.com/phpBB/viewtopic.php?p=252133#p252133
Related code: https://github.com/t-backoff/knowledgebase

I have a controller located at <ext>/kb/index.php which calls a custom HTML file located at <ext>/styles/all/template. When I enable my extension and try to call the controller using app.php?controller=kb/, I get a general error saying it can't find the HTML file. I believe the controller is fine, because if I put the file in phpBB's style template directory, my extension loads correctly.