gatsby-jsx-transform.md

Gatsby reverted support for new JSX transform (which is from React 17). If you need this, you should setup babel (and maybe typescript)

babel.config.js

module.exports = function(api) {
  api.cache(true)

  const presets = [
    [
      "babel-preset-gatsby",
      {
        reactRuntime: 'automatic'
      },
    ],
  ]

  const plugins = []

  return {
    presets,
    plugins,
  }
}

tsconfig.js

{
  "jsx": "react-jsx"
}

Also need React 17, babel-preset-gatsby >= 0.5.8.

References:

https://github.com/gatsbyjs/gatsby/tree/master/packages/babel-preset-gatsby https://devblogs.microsoft.com/typescript/announcing-typescript-4-1-beta/#jsx-factories