react-app-rewire-less

You might not need this rewire, Create React App added guide about how to add Less support to CRA without the need of ejecting. See Adding a CSS Preprocessor section of CRA guide. Also note, that their solution is based on compiling Less without using Webpack.

$ npm install --save react-app-rewire-less

• Rewire your app than modify config-overrides.js

const rewireLess = require('react-app-rewire-less');

/* config-overrides.js */
module.exports = function override(config, env) {
  config = rewireLess(config, env);
  // with loaderOptions
  // config = rewireLess.withLoaderOptions(someLoaderOptions)(config, env);
  return config;
}