The Galaxy S20 series is billed to receive additional camera improvements via a software update. Although Samsung hasn't specified what they are, user reports suggest that it has improved the camera's low-light performance. The software is only available in Korea for now and will be rolled out globally in the coming weeks.
https://www.notebookcheck.net/Latest-update-for-Galaxy-S20-series-brings-forth-better-Night-Mode-performance-and-other-camera-improvements.466146.0.html