site has been made super complicated to use
If you search from the board you want the results (as far as I have found), the search only pulls from that board. Keywords, I am not sure what you are asking for there. I recently did a search on a local board for a post I know was made a few years ago, and yes, Voila! with 3 keywords.
So, right now we are on the Site Talk board, if you use the search bar on this page, the keywords you use will only search this board, I hope that clarifies this somewhat for you.