The D-HYDROFLEX project is tackling the challenge of adapting hydropower to the changing energy landscape characterized by the integration of variable renewable sources in Europe's power grids. By utilizing advanced digital technologies and hybrid energy systems, D-HYDROFLEX aims to enhance the flexibility of hydroelectric plants to meet evolving grid demands while maintaining operational efficiency and environmental sustainability. Key innovations include integrating hydropower with hydrogen storage solutions, facilitating smoother adaptation to fluctuating grid demands, virtual power plant coordination for optimized load balancing, and AI algorithms for real-time adjustments. Real-world validation through demonstration campaigns in Greece, Spain, Romania, and France focuses on peak shaving, frequency regulation, and hybrid system optimization. The project's impact extends to supporting the EU's decarbonisation goals by improving energy security, market competitiveness, and offering decarbonised solutions. D-HYDROFLEX highlights how hydropower, through flexibility enhancements, plays a crucial role in Europe's renewable energy transition, making it a core pillar of the future energy system.