Warning: Prop `className` did not match. Using Material UI v5 with Next.js v11

import * as React from "react";
import Document, { Html, Head, Main, NextScript } from "next/document";
import createEmotionServer from "@emotion/server/create-instance";
import createEmotionCache from "../src/createEmotionCache";

export default class MyDocument extends Document {
  render() {
    return (
      <Html lang="en">
        <Head>
          {/* PWA primary color */}
          <meta name="theme-color" content={"#000"} />
          <link
            rel="stylesheet"
            href="https://fonts.googleapis.com/css?family=Roboto:300,400,500,700&display=swap"
          />
        </Head>
        <body>
          <Main />
          <NextScript />
        </body>
      </Html>
    );
  }
}

// `getInitialProps` belongs to `_document` (instead of `_app`),
// it's compatible with static-site generation (SSG).
MyDocument.getInitialProps = async (ctx) => {
  // Resolution order
  //
  // On the server:
  // 1. app.getInitialProps
  // 2. page.getInitialProps
  // 3. document.getInitialProps
  // 4. app.render
  // 5. page.render
  // 6. document.render
  //
  // On the server with error:
  // 1. document.getInitialProps
  // 2. app.render
  // 3. page.render
  // 4. document.render
  //
  // On the client
  // 1. app.getInitialProps
  // 2. page.getInitialProps
  // 3. app.render
  // 4. page.render

  const originalRenderPage = ctx.renderPage;

  // You can consider sharing the same emotion cache between all the SSR requests to speed up performance.
  // However, be aware that it can have global side effects.
  const cache = createEmotionCache();
  const { extractCriticalToChunks } = createEmotionServer(cache);

  ctx.renderPage = () =>
    originalRenderPage({
      enhanceApp: (App) => (props) => <App emotionCache={cache} {...props} />,
    });

  const initialProps = await Document.getInitialProps(ctx);
  // This is important. It prevents emotion to render invalid HTML.
  // See https://github.com/mui-org/material-ui/issues/26561#issuecomment-855286153
  const emotionStyles = extractCriticalToChunks(initialProps.html);
  const emotionStyleTags = emotionStyles.styles.map((style) => (
    <style
      data-emotion={`${style.key} ${style.ids.join(" ")}`}
      key={style.key}
      // eslint-disable-next-line react/no-danger
      dangerouslySetInnerHTML={{ __html: style.css }}
    />
  ));

  return {
    ...initialProps,
    // Styles fragment is rendered after the app and page rendering finish.
    styles: [
      ...React.Children.toArray(initialProps.styles),
      ...emotionStyleTags,
    ],
  };
};

import * as React from "react";
import PropTypes from "prop-types";
import Head from "next/head";
import { ThemeProvider } from "@mui/material/styles";
import CssBaseline from "@mui/material/CssBaseline";
import { CacheProvider } from "@emotion/react";
import { portfolioTheme as theme } from "../src/theme";
import createEmotionCache from "../src/createEmotionCache";

// Client-side cache, shared for the whole session of the user in the browser.
const clientSideEmotionCache = createEmotionCache();

export default function MyApp(props) {
  const { Component, emotionCache = clientSideEmotionCache, pageProps } = props;

  return (
    <CacheProvider value={emotionCache}>
      <Head>
        <title>My page</title>
        <meta name="viewport" content="initial-scale=1, width=device-width" />
      </Head>
      <ThemeProvider theme={theme}>
        {/* CssBaseline kickstart an elegant, consistent, and simple baseline to build upon. */}
        <CssBaseline />
        <Component {...pageProps} />
      </ThemeProvider>
    </CacheProvider>
  );
}

MyApp.propTypes = {
  Component: PropTypes.elementType.isRequired,
  emotionCache: PropTypes.object,
  pageProps: PropTypes.object.isRequired,
};