  We study the mutual relationship between dark matter-electron scattering
experiments and possible new dark matter substructure nearby hinted by the Gaia
data. We show how kinematic substructure could affect the average and
modulation spectra of dark matter-electron scattering in semiconductors, and
the discovery reaches of future experiments with these targets. Conversely, we
demonstrate how future data could probe and constrain the substructure dark
matter fraction, even when it constitutes a sub-dominant component of the local
dark matter density.
