Using F# for Desktop Apps
Option 1: Use Avalonia.FuncUI (cross-platform)
Avalonia.FuncUI is an F# Model-View-Update framework for functional cross-platform UI development.
Option 2: Use Elmish.WPF (Windows Only)
Elmish.WPF is a production-ready library that allows you to write WPF apps with the robust, simple, well-known, and battle-tested MVU architecture, while still allowing you to use all your XAML knowledge and tooling to create UIs.
Option 3: Use Windows Forms or WPF directly (Windows Only)
On Windows, F# lets you directly program Windows Forms and WPF applications directly. Some resources for doing this are below, many others are available on the web.
There are other options, see also F# Community Projects.