Hi DutchDelight,
It depends how you have set your free shipping. If it’s a shipping discount, then you can “unpublish” it from the Point of Sale channel.
Here’s how:
On the “Discounts” page in the admin, select the checkbox for the free shipping discount. Then, click the “…” button and “Deny sales channel access.”
Then, in the “Unpublish discounts from selected sales channels?” popup, select only “Point of Sale,” then click “Unpublish.”
If you’ve set up free shipping via shipping rate rather than a shipping discount, then I honestly don’t know the answer.
Hope this helps,
Tobe