I notice when I use Survey123 on the two portals that were switched with the new authentication, I don’t see the explicit login (in app) that I see with ArcGIS Pro, Portal or Dashboard.
I'm sure the survey name is unique so that's not a possible cause for me.
I’ll try to do the console logs and send it later. I’ll also try using a new computer without Survey123 and see how the connection behaves.
As to the external browser question, I have seen it once and did it once but to be honest I can’t remember if it was Survey123, ArcGIS Pro, Dashboard or any of the two Portals I have tested. I can’t repeat the sign in option again. When I see it again I’ll give an update.
THANKS!