The present study considers the dynamics of a viscous porous fluid layer in which the fluid is in local thermal non-equilibrium, obeying the Darcy-Brinkman equations in the presence of the Maxwell-Cattaneo (MC) effect. We first examine the layer's linear stability and then address the nonlinear problem numerically. The linear stability is investigated when fluid and solid obey the MC relation between the heat flux and the temperature. We first prove that the layer can support only steady convection in the absence of the MC effect. The introduction of the MC effect, whether in the solid only, in the fluid only, or in both, is accompanied by the appearance of oscillatory modes. The stability boundary of the oscillatory mode bifurcates from that of the steady through a Hopf bifurcation. The dependence of the stability boundary on the different parameters of the problem is discussed in detail. The preferred mode of convection is identified in the space of the parameters. When the MC effect is present only in the solid, the layer can support oscillatory convection if the thermal interphase interaction coefficient, H (which measures the degree of nonlocal equilibrium), is large enough. On the other hand, when the MC effect is present in the fluid only, oscillatory convection occurs for a small but non zero interaction coefficient. The presence of the MC effect in both fluid and solid introduces a new situation when oscillatory convection can occur for intermediate values of H. Besides, this study also investigated the impact of the Maxwell-Cattaneo effect on the flow and heat transfer dynamics of a porous medium in a local thermal non equilibrium (LTNE) state by focusing on the quantitative investigation of natural convection in a square porous cavity filled with water and crude oil. The Darcy Brinkman model for the fluid flow is utilized by considering the MC relation of temperature and heat flux for the fluid and solid. The role of the pertinent parameters such as the Rayleigh number, thermal conductivity ratio, Darcy number, and Brinkman number on streamlines, isotherms, and the average Nusselt numbers of fluid and solid were also investigated and discussed in detail.