_document.tsx

import Document, { DocumentContext, DocumentInitialProps } from "next/document";
import { ServerStyleSheet } from "styled-components";

export default class MyDocument extends Document {
  static async getInitialProps(
    ctx: DocumentContext
  ): Promise<DocumentInitialProps> {
    const sheet = new ServerStyleSheet();
    const originalRenderPage = ctx.renderPage;

    try {
      ctx.renderPage = () =>
        originalRenderPage({
          enhanceApp: App => props => sheet.collectStyles(<App {...props} />)
        });

      const initialProps = await Document.getInitialProps(ctx);
      return {
        ...initialProps,
        styles: [
          <>
            {initialProps.styles}
            {sheet.getStyleElement()}
          </>
        ]
      };
    } finally {
      sheet.seal();
    }
  }
}

// Source: https://stackoverflow.com/questions/67087999/how-to-properly-type-the-document-tsx-file-from-next-js