Age vs. metallicity gradients of our GC-rich LSB dwarfs, coloured as in previous figures (also NGC1052-DF2 now). Quiescent simulated cluster UDGs from TNG50 (black three-point asterisks) and the mean gradient (dashed grey) for field UDGs in NIHAO, both computed within 0.7 R_e are shown. Red three-point asterisks correspond to simulated field dwarfs from the FIRE-2 simulations; the red shaded region marks the interval considered as ‘flat’ according to Mercado et al. (2021). Pink diamonds correspond to observed classical dwarfs from the literature (see the main text). Our LSB dwarfs are compatible with being at the tail of the distribution of both observed and simulated dwarfs, around the intersection of zero–zero gradients.