One of the strange things about garlic- scapes are not always reliably present. Some varieties (Spanish Roja?) have started out as soft neck for me, but become stiff neck after some generations. I don’t think you can depend on always getting scapes from stiff neck varieties but I don’t know. But once those leaves are dying back you can start checking for harvest.
JustAnne and GroJim are right in saying that the garlic turns brown from the bottom up, whereas I said from the top down. My addled brain at work again! But I think I am right in saying that it is better, once the bottom two or three leaves are brown, to go ahead and lift the garlic, and not let the heads stand in the garden until they start to shatter.
But the heck with what I think. I searched the question and liked this article: