Microsoft made the GitHub UI significantly worse by rewriting everything in React. It's now slow and bloated. Copying text from the file viewer is a nightmare. And never ever look at how GitHub Actions work under the hood, you will wish you never became a developer.
Search is very much FUBAR. I get nagged to register even though they know I have like 17 github accounts, because who does not? They missed the ball on that one. Sometimes I like to browse without any cookies on a separate browser for window shopping reasons. Leave me alone Microsoft.
I don't think they used a framework, I remember they used a lot of "vanilla JavaScript". They're using Rails after all. Here is a thread from 2022 where they began using React for their (then) new search: https://news.ycombinator.com/item?id=33576722
