<p>This study examines the stability properties of convection patterns in a rotating Navier–Stokes-Voigt fluid layer, heated from below and saturating a porous medium. The Darcy-Brinkman model is employed to describe the fluid flow within the porous medium. A comprehensive analysis is conducted for different combinations of free and rigid boundary conditions, employing both linear and nonlinear approaches. The eigenvalue problems are formulated using the energy method and normal mode analysis, with the Galerkin method applied to determine the critical Darcy-Rayleigh numbers. The linear and nonlinear analyses give the same results, showing that subcritical region does not exist and that the system is globally stable. The study highlights the effects of rotation, medium permeability, and the Kelvin-Voigt parameter on convection behavior. Rotation and the viscoelastic parameter exhibit stabilizing effects, whereas medium permeability promotes destabilization. Additionally, rotation and permeability influence both stationary and oscillatory modes of convection, while the viscoelastic parameter specifically impacts oscillatory modes without affecting stationary convection. These findings are illustrated through graphical analysis.</p>