Honestly, easiest to learn is probably React. That + market share would make me learn that first. Newer frameworks tend to base what they do with ergonomics from React. Even my favorite (at the moment) frontend library, SolidJS, has all their tutorials with references to how you do things in React, and how similar signals work with Solid. Learning Vue, Svelte, all have the same issue; they compare themselves to React to show you how they do things with their library. And it makes sense, for better-or-worse.