https://techcrunch.com/2019/10/11/twitter-comes-back-to-the-mac/

Twitter has returned to the Mac with the debut of a new Catalyst-powered app for mac OS Catalina, launched on Thursday. The company in June had been among the first to announce its plans to take advantage Mac Catalyst — Apple’s new toolset for bringing iPad apps to the Mac desktop — following Apple’s Worldwide Developer Conference, where Catalyst had been officially introduced.

The idea with Catalyst is to make it easier for iOS developers to create software for the Mac ecosystem, by allowing them to leverage their existing iOS project and source code, then layer on native Mac features, and convert touch controls to the keyboard and mouse.