Here is an update from 3/2025. I used qt 6.8.2 and ported a simple c++ (no qml) application from Ubuntu 20 to Android. Qtcreator created the cmake based project and generated an android manifest pretty effortlessly. However, there were some bugs that had to be worked around (off the top of my head), where the issue did not occur (or apply) on the Desktop version.
QChart animation unreliable (would stop drawing before the chart is complete; had to disable)
QRadioButton seems to require forced repaint (after value updated in code, the buttons remained unchanged).
Selection of QComboBox entry by touch event does not seem to work. (seems to be an unresolved issue; Can not select qcombobox item with touch)
Mysterious / random performance issues for a subset of users (20% of my users reported taking minutes between hide and show of QDialogs; seems to be a known bug though https://forum.qt.io/topic/157681/performance-graphical-glitches-on-android
Vertical coordinate of rendered widgets requiring adjustments (being worked on by the QT Team; https://forum.qt.io/topic/160903/qt6-8-2-android-mouse-coordinates-inside-a-qdialog-window-are-wrong)
Customization of android manifest from using default icon required some manual editing of the manifest (encountered by others; https://forum.qt.io/topic/140365/how-to-set-icon-for-qt-android-app-in-cmake)
Despite the issues, the port itself should be considered reasonably straight forward and fast, for me who's never done an Android app before. Most advice I read online suggested to do the graphical presentation in QML, which I shall explore. Last but not least, I do not mean to convey misinformation, so please do forgive me if my findings are due to misunderstanding or ignorance.