Top: λ(R), axis ratio q(r) and triaxiality T(r) profiles for an example galaxy. Bottom: λ for the edge-on projection versus minor to major axis (left panels) and triaxiality parameter (right panels) in stellar mass bins. Each data point is a local measurement within a shell of major axis R = r: each TNG galaxy is represented by ∼6 data points measured between 3.5 and 8 R_e. FRs and SRs are shown with different colors as in the legend. The mass bins are labelled on the right margins. Lower rotational support λ in the stellar halos is related to rounder shapes, with a wide range of triaxiality which depends on stellar mass. FRs and SRs exhibit a continuity in stellar halo properties rather than a bimodality.