Hello! There is not currently a mechanism in ArcGIS Velocity real-time or big data analytics to remove geometry. We will add this as an idea to consider for enhancement in a future release.
For many feed and source types, you can choose to simply not configure geometry and therefore ingest tabular records. This is not an option however for Feature Layer feeds/sources, and certain Parquet files.
Thank you Peter, please do let me know if you require any use cases as motivation for this. We now have a geometry as part of our output data but it has no relevance to the accompanying data.