I go to
Stores > MyStore > Configuration > Customers > Customer Configuration > Name and Address Options
There I set Show Gender to optional.
I expect that a gender field would appear on the checkout shipping and billing address that the customer can optionally check. But nothing appears.
On the database I can see that the sales_order has a field customer_gender. So I suspect there should be a way to activate the field.
How do I insert a gender field on the checkout shipping and billing addresses?