  Sterile neutrinos with masses at the $\mathrm{keV}$ scale and mixing to the
active neutrinos offer an elegant explanation of the observed dark matter (DM)
density. However, the very same mixing inevitably leads to radiative photon
emission and the non-observation of such peaked $X$-ray lines rules out this
minimal sterile neutrino DM hypothesis. We show that in the context of the
Standard Model effective field theory with sterile neutrinos ($\nu$SMEFT),
higher dimensional operators can produce sterile neutrino DM in a broad range
of parameter space. In particular, $\nu$SMEFT interactions can open the large
mixing parameter space due to their destructive interference, through operator
mixing or matching, in the $X$-ray emission. We also find that, even in the
zero mixing limit, the DM density can always be explained by $\nu$SMEFT
operators. The testability of the studied $\nu$SMEFT operators in searches for
electric dipole moments, neutrinoless double beta decay, and pion decay
measurements is discussed.
