Posting here in case anyone is following the progress - The resolution has gone from "Potential fix identified - For a future OS update" to "Open"

Thanks for the update! I had tried with TestFlight previously and it fails to install as well. We support iOS versions 15-26 and distribute QA builds to testers via TestFlight so the only viable option at the moment is to programatically add the capability for iOS 26 only but I have not found a way to do that!

Thanks again. Resolution has been updated to "Potential fix identified - For a future OS update". Could be wrong but this may mean an Xcode update.

The resolution of FB20939056 was : Investigation Complete -- unable to diagnose its current information. I added this thread to the "add more information" for added context. I added as much information as I could.