I've been patiently waiting since 2014 for Apple to officially support swift on FreeBSD... My initial impressions with Ubuntu weren't great, to say the least. I find the operating system verbose, cluttered and needlessly convoluted as a FreeBSD user which is frustrating considering how much I love the Vapor, framework which only supports Ubuntu at the moment. This isn't a slight to Ubuntu, I know plenty of Linux users who loathe the idea of using FreeBSD lol it's all in good fun.
As an open source project, Swift coming to a broader diversity of platforms ultimately depends on people with the specific talent, expertise, and time to support those platforms.
A FreeBSD port is in need of a champion to organize the work and likely do the main heavy lifting, much as how the Windows port (which has come a long way) has been championed by @compnerd.
If a port were made to happen, as an open source community we could figure out how the port would be maintained going forward. Even in that scenario a port would benefit from having a steward who could help out in keeping the port working when new issues or requirements periodically came up.