  The investigation of distant galaxy formation and evolution is a powerful
tool to constrain dark matter scenarios, supporting and in some cases
surpassing other astrophysical and experimental probes. The recent completion
of the Hubble Frontier Fields (HFF) programme combining ultra-deep Hubble Space
Telescope observations and the magnification power of gravitational lensing
produced by foreground galaxy clusters has enabled the detection of the
faintest primordial galaxies ever studied. Here we show how the number density
of such primordial galaxies allows to constrain a variety of DM models
alternative to CDM. In particular, it provides stringent limits on the mass of
thermal WDM candidates, on the parameter space of sterile neutrino production
models, and on other DM scenarios featuring particles in the keV mass range
which is also supported by recent detections of a 3.5keV X-ray line. These
constraints are robust and independent of the baryonic physics modeling of
galaxy formation and evolution. Fuzzy DM (ultralight DM particles) results
strongly disfavored.
