When installing phpBB 4.0, installer won't recognize available DBMS drivers when they aren't pdo, and will throw error:

Supported databases

You must have support for at least one compatible database within PHP. If no database modules are shown as available you should contact your hosting provider or review the relevant PHP installation documentation for advice.

Doctrine DBAL 3.9 has built-in drivers for both type of interfaces (see https://www.doctrine-project.org/projects/doctrine-dbal/en/3.9/reference/configuration.html#configuration), which should become available after merging the patch for PHPBB-17509.