GraphiQL explorer fails to sign in because of cross-site cookie being rejected

When trying to sign into GitHub from https://developer.github.com/v4/explorer/ I get an error.

I see an error at the address https://graphql-explorer.githubapp.com/auth/github:

>The change you wanted was rejected.

>Maybe you tried to change something you didn’t have access to.

A cookie associated with a cross-site resource at https://graphql-explorer.githubapp.com/ was set without the SameSite attribute. It has been blocked, as Chrome now only delivers cookies with cross-site requests if they are set with SameSite=None and Secure. You can review cookies in developer tools under Application>Storage>Cookies and see more details at https://www.chromestatus.com/feature/5088147346030592 and https://www.chromestatus.com/feature/5633521622188032.

This is with Chrome 79 and the ‘SameSite by default cookies’ flag enabled, which will be the default in Chrome 80.