Comment 6 for bug 1288885

It's complex, so trying to explain the situation is:
- We've QT_SELECT=qt5 set globally on the device, that's why everything works there without setting anything
- 'qt5-default' depends on development files, so it can't be used by default
- qmlscene is considered 'development binary' by upstream and 'not recommended for production', and while there has been talk that we need a simple replacement for it (since what it does is relatively simple too), those plans haven't went forward AFAIK
- The reason you see 'qt4' mentioned is because that's nowadays the fallback option when there is no configuration selected, which helps eg. KDE to remain functioning similar to before

So this is the same issue as what was on device, happening on desktop. Luckily, the qtchooser offers many ways of setting the Qt version - configuration, env var, program parameter.

You should try:
'qmlscene -qt5 /usr/share/music-app/music-app.qml' for the desktop file?

The other poorer solutions include:
- Call '/usr/lib/*/qt5/bin/qmlscene' - if expansion works, that'll also works
- A more exact version of above, call '/usr/lib/$(dpkg-architecture -qDEB_HOST_MULTIARCH)/qt5/bin/qmlscene'
- Set QT_SELECT=qt5 before launching

Bonus:
- Upstream has provided a new 'qml' binary supposed to be more suitable for those uses people have used 'qmlscene' for, so you may want to experiment with 'qml -qt5 /usr/share/music-app/music-app.qml' (after apt-get install qml). It's still worth investigating at some point, since there could be eg. startup time improvement.