I am trying to install PyQt5 on my Mac but I do not know how to use it well. I have tried to install sip doing
cd ~/Downloads/sip-4.17
python configure.py
Qt has a Mac .dmg installer with all the components. I uninstalled my pip version first, and installed my Qt into the standard location - I tried putting into /opt/Qt as suggested by another post, but it failed due to changes to MacOS rights in Mojave. There is an expansion triangle next to the Qt item which allows for installing Designer separately from the Qt engine and the 2D/3D development and platform-specific tools.
Qt Installer:
https://www.qt.io/download-qt-installer