I've found that phind.com is pretty good, although I'm not sure which LLM it's backed by and I only use it for hobby projects.
> Expert mode is our most advanced searching mode, powered by GPT-4. This mode hallucinates less and writes better code. We highly recommend that you use it for advanced questions. Whenever the "regenerate" button is pressed, Expert mode is used to increase the odds of a high-quality answer.