Mine won't eat cabbage, either, even shredded for them, and they're not crazy about kale. But they LOVE wild dandelions and French sorrel best of all! And the spicy mustard-flavored Asian greens that self-sow all over the veg garden, even in the winter.
I'll have to try them on turnip greens, and the carrot greens (officially left on the carrots for "Santa's reindeer" next to Santa's cookies, so they must disappear overnight

).
But a big clump of grassy weeds, preferably with root ball attached, is always welcome. They encourage me to keep after the weeding all over the yard!