Comment 9 for bug 1251178

It's 2021, and this issue still exists.
In my case with qdbus command, installing and re-installing qt5-default does not help.
The solution of @yatsek worked:

qdbus: could not find a Qt installation of ''

$ sudo apt-get install apt-file

$ sudo apt-file update

$ apt-file search /usr/lib/qt5/bin/qdbus
qdbus-qt5: /usr/lib/qt5/bin/qdbus
qtbase5-dev-tools: /usr/lib/qt5/bin/qdbuscpp2xml
qtbase5-dev-tools: /usr/lib/qt5/bin/qdbusxml2cpp
qttools5-dev-tools: /usr/lib/qt5/bin/qdbusviewer

$ sudo apt-get install qdbus-qt5

Voila!