Just finishing off setting up ElementaryOS on my wife's early 2015 MacBook Air. It's based on Ubuntu LTS, but with a custom theme to make it macOS-esque. Seems pretty good so far, but time will tell if she enjoys using it.

Edit: Everything but the webcam just worked out of the box. The webcam was a motherfuck though. Took the better part of 3hrs trawling forums to find the full instructions for installing the kernel module to get it running....