We actually had a question similar to this in this topic, although in that case it was looking for assets that do have the agent running.
What I believe you can do is join with the dim_asset_software table and the dim_software table, then use name in the software table to see if that particular asset has a row for the “Rapid7 Insight Agent.” If your asset doesn’t have a row for the Insight agent under asset software, then it shouldn’t have the agent installed.