Receipt apps

I know that this has been brought up before, but does anyone know for sure whether we're allowed to scan receipts into various rewards apps, like Receipt Hog, Ibotta, Fetch, etc? There's nothing in our contract with Instacart that prevents us from doing this, is there? It would be nice to get get a little something extra by holding onto the receipts - but I don't want to take any risk of getting deactivated by Instacart, even if there's only a small chance that they would find out.

Also, to people who already do this - what are the best apps? I haven't used any yet, so I'm not very familiar with them. I've heard about the three mentioned above - are there others that I should look into?

I'm really only interested in using apps that are quick and straight forward. It sounds like Ibotta requires that you manually look through all of the items that you bought, checking for promotions - which sounds like more of a hassle than it's worth. So I might skip that one. But any apps where you can just scan receipts and collect points seem like they would be worth giving a try.