I'm posting this message in the forum as I lost any hope of finding a solution or workaround to the problem - hopefully someone here has already faced and solved it. Although I'm on a Galaxy Note10+, I'm pretty much convinced this issue should be reproducible in any Samsung device which has Dual Messenger enabled.
One can easily realize that beyond duplicating the supported app of interest (WhatsApp, Facebook, etc.), Dual messenger also duplicates silently in the background a significant number of other apps - you can check it in your apps list, and you'll notice the duplicates with the Dual Messenger typical overlay. I'm assuming that all such duplicates are necessary to support the Dual Messenger infrastructure behind the scenes. One of such duplicates is Google Play Services.
The issue is that such app duplication for Google Play Services creates an annoying issue with Google Prompt feature when one has Google's account phone authentication or 2-step verification enabled. Whenever I try to authenticate with Google account, a Google Prompt notification is shown in my device to verify my identity - but the notification comes twice, at the same time. It's clearly a Dual Messenger issue, as one of the notification screens has the Dual Messenger overlay.
Any thoughts - ideas, suggestions? I just wish Samsung could fix this somehow.
I have checked it now. I recieve only one prompt. Don't know your case. Check>Google two step verification settings and see, to which devices they send the prompts. Check whether it is duplicated there also.