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.