Assign different carriers to articles

[Lumière de Lune]

Hello,

I've been charged of a website that uses prestashop, and I'm facing a problem for which I can't find a solution.

We are selling online two kind of products, one is a physical product, which has to be delivered, the second one is a non physical, without delivery and without download (customers buy trees which will be planted through reforestation and carbon compensation programmes)

At first I created two different carriers, as I thought it might be possible to affect a carrier to an article but that does not work.

Then I found a "workaround", but I don't like it, because it's wrong. I said that this product is to be downloaded, and I create a certificate as "file" to be dowloaded. But that's not the real process.

I spent two days searching in this forum, and the question how to be able to affect a carrier to a product or a product family seems to come regularly. Is there really no solution ?