If chatGPT knows your IP, which it does, then it can know your location, maybe through use of a service like https://ipinfo.io
In the context of public information, our API service is used in some OSS LLM projects. I believe the intention behind using our data to contextualize interaction and the user's location background.
check your memory and open conversations, see if you ever mentioned your location. It might also have knowledge of conversations deleted within the past 30 days, but I'm not 100% sure. Possibly the search engine used your IP to get location results, and then chatgpt gathered your city from there.