Answers for "sass or scss or less for react app?"

add sass to react

npm install node-sass --save-dev

react scss sass

Note: LibSass and the packages built on top of it, including Node Sass, are deprecated. If you're a user of Node Sass, you can migrate to Dart Sass by replacing node-sass in your package.json file with sass or by running the following commands:

$ npm uninstall node-sass
$ npm install sass
# or
$ yarn remove node-sass
$ yarn add sass