At first, I downloaded entire channels, loaded them into a vector DB, and did RAG. The results sucked. Vector searches don't understand things very well, and in this world, specific keywords and error messages are very searchable.
Instead, I take the user's query, ask an LLM (Claude / Bedrock) to find keywords, then search Slack using the API, get results, and use an LLM to filter for discussions that are relevant, then summarize them all in a response.
This is slow, of course, so it's very multi-threaded. A typical response will be within 30 seconds.