  We analyze the class of models with an extra $U(1)_X$ gauge symmetry that can
account for the $b \to s \ell \ell$ anomalies by modifying the Wilson
coefficients $C_{9e}$ and $C_{9\mu}$ from their standard model values. At the
same time, these models generate appropriate quark mixing, and give rise to
neutrino mixing via the Type-I seesaw mechanism. Apart from the gauge boson
$Z'$, these frugal models only have three right-handed neutrinos for the seesaw
mechanism, an additional $SU(2)_L$ scalar doublet for quark mixing, and a
SM-singlet scalar that breaks the $U(1)_X$ symmetry. This set-up identifies a
class of leptonic symmetries, and necessitates non-zero but equal charges for
the first two quark generations. If the quark mixing beyond the standard model
were CKM-like, all these symmetries would be ruled out by the latest flavor
constraints on Wilson coefficients and collider constraints on $Z'$ parameters.
However, we identify a single-parameter source of non-minimal flavor violation
that allows a wider class of $U(1)_X$ symmetries to be compatible with all
data. We show that the viable leptonic symmetries have to be of the form $L_e
\pm 3 L_\mu - L_\tau$ or $L_e - 3 L_\mu + L_\tau$, and determine the
$(M_{Z^\prime}, g_{Z^\prime})$ parameter space that may be probed by the
high-luminosity data at the LHC.
