This link is referenced in https://yarnpkg.com/advanced/sherlock#developing-your-reproduction while I am try to develop a reproduction.
Not sure why the link isn't working, but in the meantime, I think it redirects to here: https://viko0.sse.codesandbox.io
Seems only direct navigations to https://yarnpkg.com/playground work :thinking:
Hmm that's likely Gatsby's routing going in the way
https://github.com/yarnpkg/berry/blob/0604dc3d4c67593fe954c6dd349bc963cab8786a/packages/gatsby/gatsby-config.js#L132-L137 doesn't exclude /playground.
Wanna open a PR? 馃榾