The Mi 6 was Xiaomi's flagship device for 2017. The device has had its Oreo update in the beta stage for weeks but has finally received a full, stable update. The Mi 6, Mi Mix 2, and Redmi 4X have also all had their kernel sources released by Xiaomi, with the Mi 6 also receiving Treble support via unofficial channels.
https://www.notebookcheck.net/Xiaomi-devices-receive-Oreo-Treble-support-and-have-kernel-sources-released.286836.0.html