DuoDiscover is an independent directory of apps for iPhone Duo, Apple’s first foldable. Every App Store app runs on it, but few make real use of the fold. Each listing gets one of three tiers (Built for Duo, Adapted or Compatible) and shows the source behind it: Apple, the developer’s release notes or blog, with the date it was checked. 21 apps at launch plus a launch-day tracker updated daily. Free, no account, and developers can submit their apps.