I personally consume spinach, broccoli (served with a cultured dip), baby beet greens, and chard both raw and cooked, but only kale and collards (yum) in cooked form. Cabbage in slaw, cooked form or as sauerkraut. I don’t have any thyroid issues (or kidney issues), but I don’t want to contribute to the development of it either; though I try to get iodine foods in and that too should be considered by those who are susceptible to thyroid issues (in additon to eliminating other bad thyroid foods-hello, soy), IMO.
The younger leaves would be the ones I’d use raw and the larger ones for cooking.
There’s also baked kale, Rebekah. Kale isn’t a favorite of mine, but I consume it’s family members.
Another trick I learned when researching for my husband regarding his kidney disease is if you’re going to consuem a food that is high in oxalates, then consume a calcium food with it. They then bind together instead of being released by the kidneys to produce stones when eaten independently. So since my son had stones when he was 5 and then at 7 (my hubby too had them that early inlife), I started doing this and he hasn’t had another. I also encourage my husband to do the same, but he’s not as cooperative; he’ll just avoid everything which isn’t the right answer.