To try the demo, first clone this repo.
git clone https://github.com/justswim/cra-metatag-demo.git
cd cra-metatag-demo
npm install
npm run build
node server.js
Then visit localhost:5000
in the browser. Try it in an incognito window if it is not working for you in your normal browser.
You will be able to see the server render each route, and also if you view source, you will see the metatags dynamically generated by the server.
See the associated blog post here: https://www.kapwing.com/blog/how-to-add-dynamic-meta-tags-server-side-with-create-react-app/