I think Github changed the search bar functionality.
Now when I type anything into the search bar, it defaults to searching within the repo that I'm browsing.
I want to search the entire Github in this case.
Unfortunately your request doesn't seems to be possible[1] without any extension or script that will change GitHub's functionality.
N code results in X/Y or view all results on GitHub
You can read more about this on this article:
[1] As I wrote, you might develop a small thing that will alter this behavior for you, but it doesn't seem to be possible just with GitHub.