By default, the document root of a domain in DirectAdmin (DA) has the format
/home/[your_username]/domains/[your_domain]/public_html
But in case you have to run modern PHP app like Laravel or Symfony framework (they use child public directory as their docroot). In some case, using .htaccess file to rewrite is a hacky way to solve problem (or this is the option when you don't have Admin account of DA)
So, if you have an Admin account, try this
Open menu Server Manager > Custom HTTPD Configurations, then click on your domain httpd config file, then click CUSTOMIZE
In the large textbox, add this line (remind to replace username and domain) to
|?DOCROOT=/home/[your_username]/domains/[your_domain]/public_html/public|Click SAVE to save modification. Then go to Service Monitor and reload your webservers (Nginx, Apache or OpenLiteSpeed)