FRB DM evolution with redshift continued. Both panels: average total DM–z relationship derived for TNG300-1. The mean (solid grey line), median (dotted grey line), and standard deviation (shaded grey region) around the mean of values calculated for our sightlines are shown. Left panel: compared to ⟨DM_cosmic⟩ (dashed black line), and the results of analytical studies from the literature (dashed coloured lines). Right panel: compared to results derived from other cosmological simulations in the literature (dashed coloured lines).