Build error MSB4044 when trying to create an app package using WinUI with C# in VS2026

When I try to create an app package in VS2026 for a C# WinUI project, I get the following error:

error MSB4044: The "WinAppSdkGenerateProjectPriFile" task was not given a value for the required parameter "ProjectPriIndexName".

I have already tried to troubleshoot this error by adding or modifying AppxPackage related properties, but nothing has helped so far. On the other hand, the WinUI Gallery sample project from GitHub does build and create an app package just fine on the same PC.

I'm using the following project settings:

TargetFramework: net10.0-windows10.0.19041.0

OutputType: WinExe

RuntimeIdentifiers: win-x64

WindowsPackageType: MSIX

Any ideas?