That is definitely scaly leg mites. Soaking the legs at least twice a week in warm soapy water, and using a toothbrush to gently rub the scales to loosen them helps. Dry the legs well, and apply a thick oil, such as petroleum jelly rubbing it under the scales can help. It may take weeks of treatment until you see healthy new scales come in. Here is a good link to read: https://the-chicken-chick.com/scaly-leg-mites-in-chickens/