  We report the first longitudinal/transverse separation of the deeply virtual
exclusive $\pi^0$ electroproduction cross section off the neutron and coherent
deuteron. The corresponding four structure functions $d\sigma_L/dt$,
$d\sigma_T/dt$, $d\sigma_{LT}/dt$ and $d\sigma_{TT}/dt$ are extracted as a
function of the momentum transfer to the recoil system at $Q^2$=1.75 GeV$^2$
and $x_B$=0.36. The $ed \to ed\pi^0$ cross sections are found compatible with
the small values expected from theoretical models. The $en \to en\pi^0$ cross
sections show a dominance from the response to transversely polarized photons,
and are in good agreement with calculations based on the transversity GPDs of
the nucleon. By combining these results with previous measurements of $\pi^0$
electroproduction off the proton, we present a flavor decomposition of the $u$
and $d$ quark contributions to the cross section.
