In January, Apple Inc. announced it would soon allow iPhone users in Europe to download apps from marketplaces other than its official App Store. It was a radical shift, one the European Union forced on the company through its new Digital Markets Act (DMA), a sweeping law designed to reduce the power of large tech platforms. But as Apple laid out the specifics, some of the more obvious beneficiaries dismissed the opportunity out of hand. Tim Sweeney, chief executive officer of Epic Games Inc., c...