  We propose and implement a novel test to assess deviations from
well-established concordance $\Lambda$CDM cosmology while inferring dark energy
properties. In contrast to the commonly implemented parametric forms of the
dark energy equation-of-state (EoS), we test the validity of the cosmological
constant on the more fundamental scale factor [$a(t)$] which determines the
expansion rate of the Universe. We constrain our extended `general model' for
the expansion history using the late-time cosmological observables, namely
Baryon Acoustic Oscillations (BAO) and Supernovae. As a primary inference, we
contrast the BAO compilations from the completed SDSS and the more recent DESI.
We find that the former deviates from the $\Lambda$CDM scenario at a mild $\sim
2\sigma$ level while the latter is completely consistent with the standard
picture when the dark energy properties are inferred. We find that the
posterior of the dark energy EoS is mainly constrained to be quintessence-like,
however, we demonstrate the rich phenomenology of dark energy behaviour that
can be obtained in our general model wrt to the $\Lambda$CDM.
