Disable shipping for digital products

I tried removing shipping from digital products by going to Catalog > Products > Edits in the admin panel. Then, in the "Data" tab for the product, there is a setting called "Requires Shipping" that has a Yes/No toggle. I selected "No" but the product is still requiring shipping in the checkout.
I use the Opnecart version v3.0.3.7, PHP8 on LEPM stack. Watch the below video, please. I still see the shipping methods as an option to select from for a downloadable product: https://www.youtube.com/watch?v=EiHuSj47Uuo
If I disable all shipping options, I get an error message:

There are no shipping options to the selected address. Please select a different shipping address.

You did the right thing, if all products in the cart have "Requires Shipping: No" then no shipping options should show up. I think the problem is probably checking out with Amazon -- if it's not coded to detect the products without shipping, then it may need to be modified to do that. Try using the normal "Checkout" button instead, and see if the shipping steps of checkout show up. If they don't, they you'll know it's working right, and it's just the Amazon Pay extension.

I'm not sure if there's a free fix available, but most likely not. If you need to find a developer to hire to fix it, you can post a request in the OpenCart "Commercial Support" forum, which is checked by a number of OpenCart developers. You can also try checking out the OpenCart "Partners" area.