🇩🇪Germany @richardmetzger

As an alternative to serve both you may add a symbolic link called dompurify to the directory DOMPurify, e.g.
web/libraries# ln -s DOMPurify dompurifywhich helped me to get rid of the warning

richardmetzger → created an issue.

Just installed this module and ran across the reported error.

composer require symfony/filesystem

solved it for me.