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’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.