When they say framework-agnostic they are talking about not being dependent on using React.
> Who is Franken UI for?
> Franken UI is tailored for small teams and solo developers seeking a beautiful, reliable CSS framework without the complexity of React, Vue, or Svelte. It's designed with an "HTML-first" approach, making it accessible to developers at any skill level.
> Who is Franken UI for?
> Franken UI is tailored for small teams and solo developers seeking a beautiful, reliable CSS framework without the complexity of React, Vue, or Svelte. It's designed with an "HTML-first" approach, making it accessible to developers at any skill level.
https://www.franken-ui.dev/docs/introduction
As opposed to the shadcn ui
> Which frameworks are supported?
> You can use any framework that supports React.
> Next.js, Astro, Remix, Gatsby etc.
https://ui.shadcn.com/docs