Apparently Google is working on a new OS called Fuchsia, which is not based on Linux, Android, or ChromeOS. One of the components of Fuchsia is Magenta.

I just noticed that Magenta has a UEFI-aware bootloader.

https://github.com/fuchsia-mirror/gigaboot20x6

“This project contains some experiments in software that runs on UEFI firmware for the purpose of exploring UEFI development and bootloader development.”

https://github.com/fuchsia-mirror
https://github.com/fuchsia-mirror/magenta
https://github.com/fuchsia-mirror/magenta/blob/master/docs/index.md
https://github.com/littlekernel/lk