There are fewer examples on the new website, some components disappeared, Codesandbox link was removed.
Please have a look at this website, it’s a bit ugly, and poor from designer perspective, but software engineers will actually find it useful: Formula Design System
ps. Shameless plug: either publishing atlassian-frontend source maps, or sharing them with selected vendors under NDA would be also helpful for learning purposes. I have raised this question a while ago, but I did not get satisfactionary answer: Access to atlassian-frontend source maps. Maybe you can help? 