DM-only true mass-observed richness relation for the clusters at redshift z = 0.22. The richnesses have been measured using the two corresponding hydro runs – GadgetX and GIZMO-SIMBA – and considering the three projections per cluster. The solid green lines show the linear regression model results, with the coloured corresponding shaded region indicating the 1 σ uncertainty on the intercept and slope parameters. The dotted black and magenta long-dashed lines report to the model for the true hydro and weak lensing masses, as discussed in the main text. The corresponding right sub-panels display the PDF of the observed richnesses with respect to the best-fit linear model, with the shaded regions marking the corresponding σ_{log λobs}.