In the 6G SENTINEL project, five participating Fraunhofer Institutes have developed key technologies for the impending 6G mobile communications standard, targeting further improvements in data rates, availability, accuracy, service quality and reliability of mobile communications. 6G SENTINEL did not only push existing 5G technologies further but focused also on brand new approaches that will help applications such as virtual reality, digital twins and autonomous driving achieve a genuine breakthrough with 6G. The top priorities were to exploit terahertz frequencies and develop technology for more flexible networks, in particular by incorporating satellites and flying platforms.