.NET Core 3.0具有WPF，但它仅适用于Windows平台，因此不存在对多平台的内置支持.桌面GUI.

.NET Core 3.0 has WPF but it works only for Windows platform, so there is no build-in support for multi-platform desktop GUI.

您可以尝试使用 Avalonia 来移植WPF应用程序，但我从未尝试过. Avalonia可与.NET Core 2.0，.NET Standard 2.0一起使用.

You could try port WPF application using Avalonia, but I never tried it. Avalonia works with .NET Core 2.0, .NET Standard 2.0.