There was One UI update to version 5.1a week or so ago. My phone developed an issue with WhatsApp (others see my screen as green in videocalls but evrything is alright with other apps like google meet, zoom, etc). Contacted Samsung at first, they referred me back to WhatsApp, and WhatsApp confirmed that there is an issue with the software update by Samsung team. So it might be that they recalled the update, so it disappeared from your notification? Samsung haven't made any updates to software (at least not that I am aware of).