I just got a notification from the settings app on my iPhone. I have notification previews turned off, so I can't see what the notification was about until I tap it on the lock screen.
When I do that it simply asked for my passcode then takes me into face ID section of settings.
So I don't seem to have any way of finding out what that notification was actually about. It also seems a bit suspicious because it asked me to enter my passcode. (I notice now that is ordinary behaviour when you enter the Face ID and passcode section within settings).
I thought this might have been triggered by my receiving a text message but actually I don't think it was.
One thing I think I did almost exactly the time that notification was received is add an ICS file to calendar on my Mac.
Wondered if anyone can shed any light.