Great. I'm using grep.app[1] usually as for me the GitHub search is mostly useless. Your mileage may vary though. That being said there are many other great search interfaces that I am using often when I'm trying to find solutions to common problems or specific design patterns. Chromium search[2] comes to mind, Mozilla's Firefox[3], Android[4] or of course Google[5]

[1] https://grep.app/

[2] https://cs.chromium.org/

[3] https://dxr.mozilla.org/mozilla-central/source/

[4] https://cs.android.com/

[5] https://cs.opensource.google/