Confidence contours (68 and 95%) and marginalised posterior distributions for parameters S₈ = σ₈(Ω_m/0.3)^0.5, X-ray cluster mass calibration A_TM, and SZ cluster mass calibration (1 − b), with different combinations of cluster data (for the D16 mass function), eBOSS RSD data, and Planck CMB data. The filled contours and solid lines show results for a ΛCDM model where the low-redshift amplitude of matter fluctuations is left as a free parameter; i.e. relying on the self-calibration approach. In blue, only cluster data are used as low-redshift probes, whereas we further add the eBOSS RSD data for the red contours. The dashed contours and lines are the corresponding constraints obtained when σ₈ is derived as a ΛCDM prediction. The effect of adding the eBOSS RSD data is imperceptible (blue dashed versus red dashed).