<p>We study the cosmological framework consisting of the homogeneous spacetime equipped with the dark fluid satisfying affine equation of state. This inhomogeneous equation of state (EoS) possesses constant speed of sound and may describe the hydrodynamically unstable as well as the stable fluids. We present the constraints on the isotropic and anisotropic model parameters by using the expansion rate data, BAO, supernovae type Ia (Pantheon&#xa0;+&#xa0;SH0ES) data with the CMB data. We extract the information regarding adiabatic sound speed of dark fluid using the observational constraints. The cosmological parameters describe the classically stable universe evolution within <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(1\sigma\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1</mn> <mi>σ</mi> </mrow> </math></EquationSource> </InlineEquation> limits in isotropic as well as the anisotropic model. In the anisotropic extension of the affine EoS model, the observationally constrained anisotropy parameter describes the deviation from the isotropic affine EoS model. These models of the affine EoS describe the unified scenario consisting of dark matter and dark energy domination in the past and present era respectively. Based on the observational results, we show that the anisotropy will dissipate in the asymptotic era of the anisotropic universe.</p>