eRASSl–eRASS2 variability sample selection steps. First, the eRASSl and eRASS2 source catalogs are crossmatched to identify sources detected in both (C12) or only in one eRASS (C1, C2). Then, cuts are applied to exclude spurious and extended sources. Next, 3σ upper limits for nondetections are calculated for C1 and C2 subsamples. Finally, the variability significance, S, and fractional amplitude, A, are computed. In total, 2331 sources (C1+C2: 404; C12: 1927) with S > 4 and A > 4 remain.