Copy the extension to phpBB/ext/phpbbservices/scsscompiler
Go to "ACP" > "Customise" > "Extensions" and enable the "SCSS Compiler" extension.
- French, provided by ssl: https://www.phpbb.com/customise/db/download/200181. Place the fr folder in the extension's language folder.
SCSSPHP package uses an MIT License. See /vendor/scssphp/LICENSE.md for details