Suiramus if you want to strengthen the security to the maximum by moving the Flarum files, you need to place your flarum folder above/outside public_html.
If you must to keep all Flarum files under public_html, it's easier to use our official instructions and just block access to the files with .htaccess.
If you see a blank page, there was likely a PHP syntax or include error. Check your system log files (or apache log files, or PHP log files) for the error message. One of the edited paths is likely wrong.
If you want to use absolute paths for the fromPaths() command, remove the __DIR__ . variable. __DIR__ refers to the directory of the current file and is used to create relative paths.
