  Heavily oxygen deficient NdNiO$_3$ (NNO) films, which are insulating due to
electron localization, contain pristine regions that undergo a hidden
metal-insulator transition. Increasing oxygen content increases the
connectivity of the metallic regions and the metal-insulator transition is
first revealed, upon reaching the percolation threshold, by the presence of
hysteresis. Only upon further oxygenation is the global metallic state (with a
change in the resistivity slope) eventually achieved. It is shown that
sufficient oxygenation leads to linear temperature dependence of resistivity in
the metallic state, with a scattering rate directly proportional to
temperature. Despite the known difficulties to establish the proportionality
constant, the experiments are consistent with a relationship 1/$\tau$= $\alpha
k_B T/\hbar$, with $\alpha$ not far from unity. These results could provide
experimental support for recent theoretical predictions of disorder in a
two-fluid model as a possible origin of Planckian dissipation.
