C++ Qt application on Android and iOS

As an experiment, I have a pure Qt C++ application (without QML) compiling (with cmake & ninja) and running on:

• Windows
• macOS
• Linux (ubuntu and centos/redhat)
• FreeBSD

It uses basically QMainWindow, QGraphicsItem and QDialog, iostream and a few C++ containers and iterators.

I am wondering if the port to Android is:

• possible
• easy or complex (if possible)
• and if there are examples online

The same with iOS.

Yes, it is possible. I have worked in many Qt apps developed for iOS and Android. However, never used cmake, but qmake. it is good that you started experimenting using cmake which is the future as qmake is going to be deprecated sometime in the future. Qt's official documentation started adding cmake getting started tutorial.

https://doc.qt.io/qt-5/cmake-manual.html

I would like to suggest to use Qt Quick for GUI on mobile devices.