Response from Martin Woodward, GitHub’s VP of Developer Relations:
Sorry for the inconvenience @koepnick - while searching across all repos has required being logged in for a long time, when we enhanced the search capabilities earlier in the 2023 we had to extend this to repos as well (see https://github.blog/changelog/2023-06-07-code-search-now-requires-login/).
This is primarily to ensure we can support the load for developers on GitHub and help protect the servers from being overwhelmed by anonymous requests from bots etc.
On its own, it’s not. But it’s going to be one step on the path to shit-town.