FRB DM evolution with redshift. Clockwise from top left: histogram of the probability distributions (solid coloured lines) of the total cosmological DM (), and contributions from large-scale structures (, , ) for FRBs originating at various redshifts (see Table 1 and colour bar), calculated for TNG300-1. For comparison, grey lines are new data drawn from fits to these LSS distributions. These new data are combined to create the comparison histograms for . The slight mismatch between our low-redshift TNG data and drawn values arises due to the fact that our fits slightly overestimate the probability of sightlines containing very high (≳10³ pc cm⁻³) contributions at low redshifts.