Left panel: Comparison of spectra of SN 2022ngb obtained near maximum light with spectra of the SNe IIb 1993J and 2013df, and synthetic spectra from the NLTE models of Dessart et al. (2016). The models shown correspond to a progenitor with a pre-explosion mass of 4.64 M_⊙. The rest wavelength position of Hα is marked with a dotted vertical line. Right panel: Details of the evolution of the Hα absorption. Its profile is fitted with a double-Gaussian function (blue solid line), whose individual components are shown with red solid lines.