Although Capacitor is developed by Ionic, you can use it in combination with any framework and UI library you want. In fact, Capacitor itself promotes using it with whatever framework you want.

Fonk is framework extension, and can be easily plugged into many libraries / frameworks, in this documentation you will find integrations with:

FormValidation can be used with popular JavaScript frameworks such as React, Preact, Vue, Svelte, etc.

urql is a GraphQL client that exposes a set of helpers for several frameworks.

One package to get a working GraphQL client in React, Preact, and Svelte