  A novel class of vacuum metrics expressible in analytical form was recently
found for pure $\mathcal R^2$ gravity, based on a groundwork put forth by
Buchdahl in 1962. These Buchdahl-inspired solutions offer a practical framework
for testing ${\cal R}^2$ gravity through empirical observations. Within a
subclass of asymptotically flat Buchdahl-inspired vacuum spacetimes, we
identified a parameter $\epsilon$ measuring the deviation from the classic
Schwarzschild metric, which corresponds to $\epsilon=0$. In this paper, we
employ observational data from the S2 star's orbit around Sgr A* in the Milky
Way galactic center and perform Monte Carlo Markov Chain simulations to probe
the effects of the new metrics on the orbit of the S2 star. Our analysis
presented herein reports a range at 95\% confidence level on the deviation
parameter as $\epsilon\in(-0.6690,\ 0.4452)$. While no decisive evidence either
in favor or in disfavor of the asymptotically flat Buchdahl-inspired spacetimes
has been achieved, the obtained bound is compatible with the tighter results
using other data of different nature as recently reported in Eur.\,Phys.\,J.\,C
$\bf 84$, 330 (2024). As a meaningful test probing into a strong-field regime,
our present study calls for further observations with prolonged period and
improved accuracy in order to tighten the bound for $\epsilon$ using the S2
star orbit.
