  We employ a sample of 135,873 RR Lyrae stars (RRLs) with precise
photometric-metallicity and distance estimates from the newly calibrated
$P$--$\phi_{31}$--$R_{21}$--[Fe/H] and $Gaia$ $G$-band $P$--$R_{21}$--[Fe/H]
absolute magnitude-metallicity relations of Li et al., combined with available
proper motions from $Gaia$ EDR3, and 6955 systemic radial velocities from
$Gaia$ DR3 and other sources, in order to explore the chemistry and kinematics
of the halo of the Milky Way (MW). This sample is ideally suited for
characterization of the inner- and outer-halo populations of the stellar halo,
free from the bias associated with spectroscopically selected probes, and for
estimation of their relative contributions as a function of Galactocentric
distance. The results of a Gaussian Mixture-Model analysis of these
contributions are broadly consistent with other observational studies of the
halo, and with expectations from recent MW simulation studies. We apply the
HDBSCAN clustering method to the specific energies and cylindrical actions
($E$, J$_{r}$, J$_{\phi}$, J$_{z}$), identifying 97 Dynamically Tagged Groups
(DTGs) of RRLs, and explore their associations with recognized substructures of
the MW. The precise photometric-distance determinations ($\delta\, d/d < 5$\%),
and the resulting high-quality determination of dynamical parameters, yield
highly statistically significant (low) dispersions of [Fe/H] for the stellar
members of the DTGs compared to random draws from the full sample, indicating
that they share common star-formation and chemical histories, influenced by
their birth environments.
