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The emergence of lead-free halide double perovskites exhibiting bandgaps within the visible spectrum represents a substantial advancement in engineering environmentally benign perovskite solar cells. In this work, we investigated the structural, optical, electronic, and mechanical properties of Cs-based lead-free Cs2 LiGaBr6 double halide perovskites with Mn and Cr doping under hydrostatic pressure ranging from 2 to 80 GPa using density functional theory (DFT). The introduction of dopants consistently alters the lattice parameters because of the mismatch in atomic radii, whereas increasing the pressure leads to a reduction in these constants. All the studied Cs2 LiGaBr6 compounds exhibited direct band gaps, which increased slightly with doping. This is attributed to the modulation of electronic states by dopant-related defect levels. The bandgap variation under pressure is primarily attributed to changes in the quantum confinement effects induced by compressive strain. Analysis of the density of states and optical properties revealed enhanced absorption in the visible spectrum for the doped compositions, and in the UV spectrum under pressure. The study of mechanical stability confirms the ductile nature of both the doped and pristine compounds under pressure, underscoring their suitability for thin film production. This study contributes to the understanding of sustainable alternatives for perovskite optoelectronic applications, emphasizing Cs2 LiGaBr6's potential under diverse conditions and dopant influences. [ABSTRACT FROM AUTHOR]