Unfortunately nothing new or productive to add to the forum except that there's others affected too as indicated by this alternative Discussion: https://discussions.apple.com/thread/251954743
I actually contacted Apple Support via chat and after the cursory checks they referred me to the banking institution behind the Apple Card (saw that one coming). Reached out to them also via chat and was assured everything was good there. The most interesting thing I got from that conversation is that if the bank requires verification it's done through text and/or email. And if, like myself, you guys are seeing the typical "Apple Security" pop-up window - that 100% rules it out as a banking institution issue.
So I reached back out to Apple Support - this time via phone call. Spoke with the initial Tech Support Advisor who checked the things and got me in touch with a Sr Advisor. That's where we hit a brick wall. Their initial trouble shooting step was to remove my partner from Family Share and then test the theory.
Here's what I know about these verifications:
-They aren't required for free downloads
-They seem to only come up if it's an actual monetary transaction that needs to be approved
-They seem to only come up when my Apple Card is set as my primary payment method
With that information I told the Sr Advisor I'd complete their proposed steps but wouldn't be able to test functionality because there was nothing we wanted to spend money on at the time. So unless Apple wanted to spot us $5 for an app to purchase testing would have to wait. We all know that answer.
So I did the proposed step which was a pain. Got my partner re-added to Family Share with all the necessary setup and ensuring she wouldn't lose access to her iCloud Storage, apps, etc. And now we wait. I 100% do not believe this will be successful but I can't prove anything.
Here's my update and I hope it adds some validity to the issue we're seeing.
Question: Does anyone else have experience using another non-debit/bank account linked credit card? That's the only variable I have not tested as any other card I've ever used as been my typical attached-to-my-bank-VISA-debit card. Wondering if this type of issue/security would exist on another standard interest loading credit card.