The IntersectionObserver API is not available on Safari v3.1-12. Either you or any of your libraries is using this API. To make it work on older versions of Safari, you need to polyfill it. Something like this should do the job for Safari v6+:

// pages/_app.jsx

import Script from 'next/script';

const App = ({ Component, pageProps }) => (
  <>
    <Script
      src="https://polyfill.io/v3/polyfill.min.js?features=IntersectionObserver"
      strategy="beforeInteractive"
    />
    <Component {...pageProps} />
  </>
);

export default App;

References:

• https://caniuse.com/intersectionobserver
• https://nextjs.org/docs/basic-features/supported-browsers-features#custom-polyfills
• https://github.com/w3c/IntersectionObserver/tree/main/polyfill
• https://nextjs.org/docs/basic-features/script#loading-polyfills
• https://nextjs.org/docs/advanced-features/custom-app