Recent Update Broke MVNO US Mobile and Networking

I'm running the latest Bookworm, originally dist-upgraded from stable. An update approximately 2 to 2-1/2 weeks ago broke operation with my US Mobile cellular provider. Previously, the status banner icon reported "US Mobile" (an MVNO) as my carrier. Now it reports "T-Mobile" (which is the network used with US Mobile MVNO's "White" SIM cards--the US Mobile "black" card is the Verizon system).

I can no longer use cellular data at all. All web requests are re-routed to a T-Mobile page that reports that I need to subscribe to data. My online US Mobile account page reports that I have plenty of data remaining. Voice and SMS text still work but I can no longer connect to the Internet via wifi for web or apt-get update / upgrade / dist-upgrade without disabling Mobile data service first, because the requests are routed through cellular mobile service instead of wifi. Previously, wifi data had priority over cellular data.

My wife's Pinephone, also running Bookworm but not updated regularly functions with US Mobile as it should. We have the same plan.

Booting to an old version of Mobian from megi's multiboot SD card also results in correct function with US Mobile.

I consider this to be CRITICAL bug. Even though I had access to the old Mobian bug reporting system and I have a Gitlab account, it took over a week for approval to make this post!

I'm thinking that I'll have to save my /home directory and restore my system with an image from my wife's phone and then adopt her approach of avoiding Mobian updates. It's either that or I'll checkout how Manjaro is coming along, which is what shipped on my Convergence edition Pinephone when I purchased it. Hopefully this bug can be assigned and addressed before I resort to wiping my phone.