Constraints on the growth index γ for the ΛCDM cosmological model. We present the confidence ellipses obtained in the Ω_m − γ plane with eRASS1 clusters combined with sound horizon priors (in orange) and with the full likelihood from Planck20 (in red). The gray dashed line represents the prediction of γ = 6/11 from general relativity. The contours are the 68 and 95% confidence levels. The eRASS1 contours are compared with the galaxy clustering constraints from the Baryon Oscillation Spectroscopic Survey (BOSS) combined with CMB from WMAP and SNIa data (Samushia et al. 2013 in red), or combined with Planck Collaboration XIII (2016) (Beutler et al. 2014; Gil-Marín et al. 2017). We also show the SPT cluster counts results combined with BAO, SN, and CMB data (Bocquet et al. 2015) in pink.