Avalonia UI - XPF
avaloniaui.net
Cross-Platform WPF for Linux, macOS, iOS, Android and Browser. Take your WPF to new platforms with little to no changes required.

This is not to be confused with the Avalonia UI framework which remains free and open source.

XPF is a new project by the same team that allows existing WPF apps to be cross-platform (so enterprises can take their existing Windows-only apps and run them on MacOS, Linux and maybe WebAssembly). It’s in early stages so I don’t know how well it works.