Study of the CKM angle γ sensitivity using flavor untagged decays *Supported by National Natural Science Foundation of China (NSFC) (11925504, 11975015); the 65th batch of China Postdoctoral Fund; the Fundamental Research Funds for the Central Universities, CNRS/IN2P3 (France), and STFC (United Kingdom) national agencies. Part of this work was supported through exchanges between Annecy, Beijing, and Clermont-Ferrand, by the France China Particle Physics Laboratory (i.e. FCPPL). (February 2021)