The investigation of dark energy models outside of general relativity and mainstream cosmology has been driven by observational evidence of the universe's accelerating expansion. In this work, we create a new Barrow–Ricci–Gauss–Bonnet holographic dark energy (BRGB–HDE) model in the context of symmetric teleparallel gravity, in which the non-metricity scalar Q is used to characterize gravity via f(Q). The suggested scenario easily unifies holographic dark energy corrections resulting from curvature invariants with the geometric consequences of non-metricity by integrating Barrow's entropy deformation parameter Δ . This results in a more comprehensive description of cosmic acceleration. We study the model's cosmic dynamics by examining various forms of interaction between dark energy and dark matter, which allows for energy exchange within the dark sector. To assess the model's physical viability and stability, the evolution of important cosmological parameters such as the equation of state and the squared speed of sound is examined. We recreate the f(Q) function that aligns with the hypothesized holographic dark energy density and interaction method. Furthermore, the generalized second law of thermodynamics (GSLT) is investigated using the Barrow entropy formalism, with the apparent horizon of the Universe taken into account. Our findings show that the GSLT is still valid for a wide and physically tolerable range of model parameters. Notably, the model demonstrates smooth transitions between the quintessence and phantom regimes, demonstrating its ability to simulate various stages of cosmic evolution. The suggested BRGB-HDE model in f(Q) gravity offers a consistent and thermodynamically plausible framework for understanding late-time cosmic acceleration.