  In this paper, we investigate a low-order robust numerical method for the
linear elasticity problem. The method is based on a Bernardi--Raugel-like
$\boldsymbol{H}(\mathrm{div})$-conforming method proposed first for the Stokes
flows in [Li and Rui, IMA J. Numer. Anal. {42} (2022) 3711--3734].Therein the
lowest-order $\boldsymbol{H}(\mathrm{div})$-conforming Raviart--Thomas space
($\boldsymbol{RT}_0$) was added to the classical conforming
$\boldsymbol{P}_1\times P_0$ pair to meet the inf-sup condition, while
preserving the divergence constraint and some important features of conforming
methods. Due to the inf-sup stability of {the} $\boldsymbol{P}_1\oplus
\boldsymbol{RT}_0\times P_0$ pair, a locking-free elasticity discretization
{with respect to} {the Lam\'{e} constant $\lambda$} can be naturally obtained.
Moreover, our scheme is gradient-robust for the pure and homogeneous
displacement boundary problem, that is, the discrete $\boldsymbol{H}^1$-norm of
the displacement is $\mathcal{O}(\lambda^{-1})$ when the external body force is
a gradient field. We also consider the mixed displacement and stress boundary
problem, whose $\boldsymbol{P}_1\oplus \boldsymbol{RT}_0$ discretization should
be carefully designed due to a consistency error arising from the
$\boldsymbol{RT}_0$ part. We propose both symmetric and nonsymmetric schemes to
approximate the mixed boundary case. The optimal error estimates are derived
for the energy norm and/or $\boldsymbol{L}^2$-norm. Numerical experiments
demonstrate the accuracy and robustness of our schemes.
