  Kurie-plot experiments allow for neutrino-mass measurements based on
kinematics in an almost model-independent manner. A future tritium-based
KATRIN-like experiment can be sensitive to light sterile neutrinos with masses
below 18 keV, which are among the prime candidates for warm dark matter. Here
we consider such keV neutrinos in left--right symmetric extensions, i.e.
coupled to right-handed currents, which allow for an enhanced contribution to
beta decay even for small active--sterile mixing, without violating
astrophysical X-ray constraints. The modified spectral shape is in principle
distinguishable from the standard contribution---especially for sterile
neutrino masses below 9 keV, which can lead to a distinct peak. We compare the
sensitivity to constraints from the LHC and neutrinoless double beta decay.
