For code search, I've heard Hound is pretty good but I haven't personally tried it yet. The UI is a bit clunky though. I'm wondering if one can port the old Apache-licensed Sourcegraph UI? https://github.com/hound-search/hound
I have ran Hound in my current co for about 2 years now, it's fine but the search experience is far below the SG one. SG is a far superior option but it is prohibetively expensive. I thought about hacking on Hound to be honest to rewrite the UI at least because half of it is broken.