I've used pyinstaller on Wine in order to make Windows executables from Linux. Haven't figured out yet how to cross-compile for OSX yet, but that at least reduces it from requiring three major OSes to build to two.
Other than promoting Python and "diversity", what exactly does PyBee/BeeWare do? It sounds like an SDK, but it appears to just point to a bunch of random GitHub projects. It's not very clear to me.
We have low interest in Windows support for our software so I haven't even tried yet but WINE is a good idea if it works. For MacOS a TravisCI Mac build should do the trick. It'd be nice if it could all be done in a single run..., but it doesn't seem possible.
