UV bump (B) as a function of the oxygen abundance (12 + log(O/H)). Stars represent individual measurements from our subsample of sources with oxygen abundance measurements, with 1σ uncertainties derived through a bootstrapping method. For reference, the solar oxygen abundance is {12 + log(O/H)_⊙ = 8.69 (dotted blue line; Allende Prieto et al. 2001). The MW oxygen abundance is in the {12 + log(O/H) ∼ 8.24-8.76 range, depending on the Galactic radius (horizontal blue strip; Pilyugin et al. 2023). Literature results for low-z (Russell & Dopita 1992; Hunt et al. 2019; Decleir et al. 2019) and intermediate-z (Shivaei et al. 2020a) sources are shown as blue and green symbols, respectively.