In various extensions of the Standard Model (SM) that incorporate an additional \(U(1)^{\prime }\) gauge symmetry, the dark photon ( \(A^{\prime }\) ) emerges as a compelling candidate for dark matter. This hypothetical particle can interact with Standard Model particles via kinetic mixing with the standard photon, thus serving as a potential portal to the dark sector. Theoretical interest in dark photons is driven by their potential to explain dark matter’s observed gravitational effects and their implications for new physics beyond the SM. Nuclear reactors, being intense sources of photons, provide a promising environment to search for dark photons. Reactor-based experiments offer unique opportunities to study these interactions, significantly enhancing our ability to probe the fundamental properties of dark matter. A particularly effective approach is to investigate Compton-like scattering processes, facilitating both the production and detection of dark photons through electron interactions. These interactions are particularly promising to study because they could yield observable signals in the form of ionization events within the sub-keV energy range, where modern detectors, such as high-purity germanium, are highly sensitive. In this work, we investigate dark photon interactions and present preliminary constraints on the coupling strength and mass of the dark photon at the 90% confidence level, using sub-keV threshold data collected with a germanium detector at Kuo-Sheng Neutrino Laboratory, Taiwan.