So, the main use case of this is for writing Electron apps, the biggest benefit of Electron is having cross-platform apps, using swift code in your Electron app that's only work on macOS gonna defeat of propose of an Electron app.
Nope! It's entirely unremarkable on Linux (in a good way: you wouldn't notice that it's not its "native" platform), and it's surprisingly pleasant to use (and probably the easiest way to get a good C compiler) on Windows.