Distribution of the total metallicities in the neutral ISM for the Milky Way (from De Cia et al. 2021) and the Magellanic Clouds measured in this work (top panel, shaded regions). For each of the three environments, the expected distribution (if the ISM total metallicities were the same as in hot stars) is shown by a Gaussian curve centred on the hot-star metallicity and with a σ equal to the mean of the uncertainties in [M/H]_tot that we measured. The values of metallicity in the Milky Way ISM measured by Ritchey et al. (2023) are consistent with solar metallicity, with a standard deviation of ~0.1 dex, and are not shown in this figure. The bottom panel shows the cumulative distribution function of the observed total metallicities.