alt Hacker NewsGitHub Code Search has too many quirks compared to the zoekt powered alternatives (cs.android.com, cs.bazel.build) which feel far more intuitive.
I wish Microsoft would invest more in improving it - especially since Sourcegraph can't search private repositories, leaving GitHub's tool as the only real option for many codebases.
None of Google's public source search engines (android, chromium, bazel) use Zoekt. They use Google's web indexing technology adapted for trigrams, which was mostly developed to support their massive internal monorepo, but exposed for a few of their major open source projects too.
You can index private repos with Sourcegraph, but it's a paid feature ($19/mo/user+).