Missing logos from GTK apps on a KDE installation

I don't know if it's an inherent bug of libadwaita or if it's something that isn't pre-installed on a KDE installation (like Kvantum) or if it's something that I messed up (doubt), but some apps that are pre-installed like those two and Bazaar (and really, other GTK ones) have the same issue where not all icons appear. What to do in this case?