Epic Games' NBA 2K21 on Steam?

I downloaded NBA 2K21 from Epic Games a few days ago because it's free there at the moment. Today the download was finished and I had to find out that the PS4 controller is not supported by Epic Games at all. With DS4Windows as an example I don't get any further either, because the controller is not recognized there. I have now bought NBA 2K21 through mmoga so that I can play it on Steam, as they support the PS4 controller. Since I don't really want to wait another 2 days for the download, I had the question of whether I can transfer the already downloaded file from Epic Games to Steam?

Unfortunately, it is not possible that you can transfer purchased games from other launchers to another.

Not at all. Epic wants you to use their launcher so that you can create your games collection there. If there's NO Steam code for you, and no program will do that, it will not work as a natively recognized game.