Edit:
Since theres been some confusion with dates
In 2016 github made site side searching login only and hid the search bar if you werent logged in. This didnt include searching within a repository so that could still be done, just not all repositories
This year was the change being referred to in this link which made repository level searching require logging in
Blog post: https://github.blog/changelog/2023-06-07-code-search-now-requires-login/
I’ll do one drastic, but not unthinkable, example. The Signal messenger source is on GitHub. You can’t imagine a single oppressive government out there that would be keenly interested knowing who in their country is interacting with it? Or maybe you haven’t noticed that there are a lot of countries not too keen on encryption, trying to backdoor everything or just straight-up outlaw encryption. This isn’t just about a single login box. “Who’s looking at what” is the kind of surveillance that blacklists thrive on.
And please don’t come back with “then use a fake email”. Once you’re that far gone, you’re definitely breaking a user’s “core experience”.
I’m clearly using GitHub wrong if the search feature is that important.
Just download the code. You don’t have to be logged in for that (that would be more of an example of enshitification). Then you can search it however you want.