The Qt library is used to build the UI for Wireshark and is used to provide a platform independent UI. Wireshark can be built with Qt 5.3 or later.
For more information on the Qt libraries, see Section 12.2, “The Qt Application Framework”.
Most Linux distributions provide Qt and its development libraries as standard packages. The required libraries and tools will likely be split across several packages. For example, building on Ubuntu requires qttools5-dev, qttools5-dev-tools, libqt5svg5-dev, qtmultimedia5-dev, and possibly others.
The Qt Project provides an installation tool for macOS, similar to Windows. It is available at https://www.qt.io/download-open-source/#section-2.
Qt5 must be installed manually from the Qt installers page https://www.qt.io/download-open-source/#section-2 using the version of Qt appropriate for your compiler. Note that separate installations (into different directories) of Qt are required for 32 bit and 64 bit builds. The environment variable QT5_BASE_DIR should be set as appropriate for your environment and should point to the Qt directory that contains the bin directory, e.g. C:\Qt\5.15.2\msvc2019_64.