XFLEX HYDRO demonstrators grid services assessment and Ancillary Services Matrix elaboration. - Christophe Nicolet; Matthieu Dreyer; Christian Landry; Sébastien Alligné; Antoine Béguin; Yves Vaillant; Stefan Tobler; Goekhan Sari; Grégory Païs; Matteo Bianciotto; Steve Sawyer; Richard Taylor; et al. (CoRR, 2024)