Metallicity [Fe/H] plotted against the frequency of maximum oscillatory power ν_max for known oscillating stars, adapted from the left panel of Fig. 2 from Huber et al. (2024). The shaded area represents the region of evolved RGB stars, with a boundary set at ν_max ≲ 100 μHz. Noteworthy low-metallicity sub-giant branch (SGB) and RGB stars for which asteroseismic modelling has been performed are highlighted. Note that EPIC206443676 was modelled using the global asteroseismic parameters (Deheuvels et al. 2012), not the individual frequencies as in all other displayed cases. The red stars indicate the two giants considered in the present work.