You can use these CSS code to Website Tools > Custom CSS to disable/or hide/or remove Quantity
#1. All Products
div.product-quantity-input {
display: none !important;
}
#2. Products belong specific Shop Page Only
First, find Shop Page ID.
In my example, it is: #collection-667f8bab720ee26389417857
Next, replace # with dot body. so new ID will be
body.collection-667f8bab720ee26389417857
Next, use CSS like this
body.collection-667f8bab720ee26389417857 div.product-quantity-input {
display: none !important;
}
#3. Product belongs specific Category
We can’t target tag, so you need to create a tag with name: no quantity and assign it for products.
Next, use CSS code like this
/* hide quantity */
.tag-no-quantity .product-quantity-input {
display: none !important;
}