  In this paper we study an su$(m)$-invariant open version of the
Haldane-Shastry spin chain whose ground state can be obtained from the chiral
correlator of the $c=m-1$ free boson boundary conformal field theory. We show
that this model is integrable for a suitable choice of the chain sites
depending on the roots of the Jacobi polynomial $P_N^{\beta-1,\beta'-1}$, where
$N$ is the number of sites and $\beta,\beta'$ are two positive parameters. We
also compute in closed form the first few nontrivial conserved charges arising
from the twisted Yangian invariance of the model. We evaluate the chain's
partition function, determine the ground state energy and deduce a complete
description of the spectrum in terms of Haldane's motifs and a related
classical vertex model. In particular, this description entails that the
chain's level density is normally distributed in the thermodynamic limit. We
also analyze the spectrum's degeneracy, proving that it is much higher than for
a typical Yangian-invariant model.
