It is the same problem to "Black text on black background" issue, but mine is not be resolved when update the software version (now build number is N960FXXS3CSFC ).
It will happen with theme which write text on notification dialog.
I'm not OP, but I'm having the same issue and I don't have any themes. I tend to see the all white notification with the Nest app. I've tried changing many different settings. I've seen from other forums it is an issue that seems to be with the new Samsung Galaxy phones. I'm using S10+ SM-G975U with VZW.