Flavour anomaly updates from ATLAS and CMS

The latest results on flavour anomaly from ATLAS and CMS are here presented. Four recent studies are discussed: the first CMS search for the $\tau \to 3 \mu$ decay, the CMS angular analysis of the $B^+ \to K^+ \mu^+\mu^-$ decay, and the $B^0 \to K^{*0} \mu^+\mu^-$ angular analyses by ATLAS and CMS, with respective HL--LHC projections. This last study is of particular interest, due to indications of discrepancy with respect to the Standard Model from previous measurements by LHCb and Belle. All results presented in these proceedings are in agreement with the Standard Model.