The most travelled route into tech from Solvay Brussels School of Economics and Management is business and management. The route whose people most often go on to found a company is marketing and communication.
Counted from the 136 people on this wiki who list Solvay Brussels School of Economics and Management in their education, one entry per person per field. Everyone counted is already in Belgian tech, so these shares describe the routes taken by people who arrived, not the odds of arriving.