For Windows there's a 5 year old blog post: https://www.swift.org/blog/swift-on-windows/
For Linux there's a guide for GNOME: https://www.swift.org/blog/adwaita-swift/
It would be really nice if instead we could just do one style of development and then ship a set of libraries as used to work for OpenSTEP (which was why it had "OPEN" in the name).
https://www.swift.org/install/windows/
Which GUI toolkit(s) does that install support?
https://www.swift.org/install/windows/