There is no royalty on your use of Unreal Engine 4 for production of your friend’s video. There is a 5% gross revenue royalty after the first $3,000.00 of revenue is collected royalty free per quarter on any form of monetization of your friend’s game. The process by which your friend will report and pay the royalty is covered in the Unreal Engine 4 EULA and FAQs. You will find the FAQ here: Frequently Asked Questions - Unreal Engine
Thanks for the answer, but I think I didn’t explain it properly
I will create a trailer with unreal but the project is about a card game not made in unreal.
Is there still royalty?
If you are talking about a physical card game and not a video game; There is no royalty to use UE4 to create a linear video trailer (like on YouTube) for a product.