Qt 5.9 is now on FreeBSD according to developers Tobias and Raphael. Qt is an open-source application framework for developing application software. You may download it from the FreeBSD ports tree.
With Qt 5.9, the Elisa music player works, for instance (where it has run-time errors with Qt 5.7, even if it compiles). The KDE-FreeBSD CI system has had Qt 5.9 for some time already, but that was hand-compiled and jimmied into the system, rather than being a “proper” ports build.