Hello Everyone,
I am the author of the thesis Swift for Embedded Systems mentioned in this thread. After a long time, I finally got back to working on it so I would like to share some progress with you 
- It is still in an early phase, but I am currently not aware of any bugs (but there are some, for sure
). - The toolchain itself now supports any thumbv7m or thumbv7em-based device.
- I managed to reduce the code size of a "Hello World" app down to one megabyte, which is still not great, but it means any board with 2MB of FLASH can be used comfortably to run quite a big program! That was my goal, as such boards are generally available.
- I am currently focusing on supporting the STM32F439ZI (NUCLEO-F439ZI), but adding support for any other board from the STM32F4 family should be very easy.
- I added support to the Swift Package Manager, so you can organize your code to packages as you are used to :).
- Tooling is important, so I added support to sourcekit-lsp too! :)
And the most important thing – everything is now open-sourced on GitHub and contributions are welcome! 
Let me know what you think! 