The Stylo theme was a classic desktop theme for PHP-Fusion version 7 and 8. PHP-Fusion 9 comes with themes that are following the modern responsive design. Some users prefer the classic desktop design of Stylo, and in my experience it is mostly users on mobile who prefer Stylo.
On Github I placed a version of Stylo that works on PHP-Fusion version 9.
Take a look at Github for Stylo.