  Cross-correlations between the lensing of the cosmic microwave background
(CMB) and other tracers of large-scale structure provide a unique way to
reconstruct the growth of dark matter, break degeneracies between cosmology and
galaxy physics, and test theories of modified gravity. We detect a
cross-correlation between DESI-like luminous red galaxies (LRGs) selected from
DECaLS imaging and CMB lensing maps reconstructed with the Planck satellite at
a significance of $S/N = 27.2$ over scales $\ell_{\rm min} = 30$, $\ell_{\rm
max} = 1000$. To correct for magnification bias, we determine the slope of the
LRG cumulative magnitude function at the faint limit as $s = 0.999 \pm 0.015$,
and find corresponding corrections on the order of a few percent for $C^{\kappa
g}_{\ell}, C^{gg}_{\ell}$ across the scales of interest. We fit the large-scale
galaxy bias at the effective redshift of the cross-correlation $z_{\rm eff}
\approx 0.68$ using two different bias evolution agnostic models: a HaloFit
times linear bias model where the bias evolution is folded into the
clustering-based estimation of the redshift kernel, and a Lagrangian
perturbation theory model of the clustering evaluated at $z_{\rm eff}$. We also
determine the error on the bias from uncertainty in the redshift distribution;
within this error, the two methods show excellent agreement with each other and
with DESI survey expectations.
