This is a WPF .NET 6.0 application with a modern user interface library (WPFUI). There is a known issue where the project fails to build due to duplicate reference issue (https://github.com/dotnet/core/blob/main/release-notes/6.0/known-issues.md#issues-building-wpf-application-with-windows-desktop-607-and-608).
This problem has been permantely patched in the project files. However, you might experience invalid InteliSense issues. This does not affect the build at all.