There are a website called https://www.17ce.com/, it's a speed test service, but their server mainly located in China (Of course, it's a Chinese website), so it can be used to test status of some GFW blocks.

That website tells me GitHub is fine, and that's all, I guess.

This is the speed test result for Google.com https://imgur.com/eOoxthu

This is the result for GitHub.com https://imgur.com/T9o0U79 (Red == Delay was very bad)