1-, 2- and 3-sigma contours of the emcee regressions in the slope-normalization () plane of the L_X − L_UV for both data and models, normalizing all L_X and L_UV to the corresponding median values of XMM-XXL. Dark green contours are related to the cleanest XMM-XXL sample (Appendix B) and the light green ones to the RM-QSO sources. The contour of the models are color coded for μ = [0, 0.2, 0.4, 0.5, 0.6, 0.8, 1], as shown in the legend. For simplicity, we report for each μ only results obtained with a single f_max, corresponding to the highest r²-score, and fixed α₀ = 0.02. Models that reproduce the observed slope are also the ones that show weaker coronae (lower normalization ).