Does SAMSON launch in Release mode?
Could you, please, try adding into the SAMSON-Core.sh script for SAMSON-Debug the a path to Qt platforms (/home/bomble/Qt5.9.3/5.9.3/gcc_64/plugins/platforms) to the LD_LIBRARY_PATH environment variable:
which should provide a path to platforms ("xcb" including).
Do you have any Python installed with PyQt5 and their paths set into PATH or LD_LIBRARY_PATH ? The platforms and Qt libs from Python installation may interfere.