Perhaps you’re already familiar with it, but Discourse kind of does this already. When you start a topic, it automatically returns search results based on what you are describing.
The next stage of solving that problem would be helping the user describe their problem more accurately. This is where I think LLMs could provide simple feedback like “you might get better help if you include a code snippet that shows what you have done so far”. Perhps this could even be a followup PM to the user if their topic has no replies after a few days.