A Microsoft platform for building and publishing apps for Windows devices.
The problem has finally been solved by upgrading Microsoft.UI.Xaml from 2.6.0 to 2.6.1. The app is the only one in the solution using Microsoft.UI.Xaml.
Apparently, the problem was caused by the recent upgrading of Microsoft.UI.Xaml from 2.5.0 to 2.6.0. In other words, Microsoft.UI.Xaml 2.6.0 was likely the culprit.