@Laëtitia
Great! Sorry for this issue!
It is due to Qt debug libraries not being shipped together with SAMSON-Debug because they are too heavy. That's why you need to install Qt and apart from providing a path to Qt libraries themselves it is sometimes necessary to provide a path to the plugins folder (Qt5.9.3/5.9.3/gcc_64/plugins, subfolders platforms and xcbglintegrations in particular).
What can also be done instead of creating symbolic links is to provide these paths in your ~/.bashrc file (this works for me on Ubuntu)
QT_VERSION=Qt5.9.3/5.9.3
export QT_PATH=$HOME/$QT_VERSION
export QT5_CMAKE_INCLUDE_DIR=$QT_PATH/gcc_64/lib/cmake/
export QT5_PLATFORM_LIBRARY_PATH=$QT_PATH/gcc_64/plugins/platforms/
export LD_LIBRARY_PATH=$QT5_PLATFORM_LIBRARY_PATH:$LD_LIBRARY_PATH