Mobile authenticator will not complete setup

I had been using a key fob authenticator, but it has begun giving a “batt 00” warning, so I’ve been trying to set up the Mobile Authenticator. I have a Galaxy S8+, running Android 9. The app will install, and will allow me to input my login info, but then stalls out at “Setting Up…” with a spinning Battle-dot-net logo. I have tried every suggestion on this Blizzard support page numerous times, all to no avail. I have submitted several support tickets through a few different media (in game, email, live chat). Each time, I’m contacted by a friendly and helpful CSR who walks me through all of the steps I’ve already gone through on the aforementioned support page, then goes off to consult with a tech. When they return, the tech’s advice is “wipe & factory reset your phone”, “use a different device”, or quite bluntly “buy a new phone”.
None of these options are appealing, to say the least. Is there really no means of diagnosing why this software will not operate correctly on my phone? What’s more, the mobile authenticator software doesn’t appear to have been updated in well over a year – before, in fact, the public release of this latest version of the Android OS. Is there still a development team supporting it?
I apologize; my frustration is seeping through into the tone of my post. I’m simply trying to understand why I’m having such difficulty getting a) this software to function properly, and b) useful assistance in achieving that end. Is there truly no resolution to this situation other than “your hardware is incompatible with our software”?