Project Treble is probably one of the best things to come out of Google for a while, and we wrote about it at length here and here. Very simply put, Project Treble is a way to separate the base Android OS framework in a module, away from everything else the chipset manufacturers, OEMs, and carriers add to Android. This simplifies a lot of things, like porting stock Android Oreo for multiple devices that support Treble, and it should speed up the way Android devices receive updates from Google and from the manufacturer.
This is why we see a lot of people asking if their devices would get Treble support. Officially, Project Treble can only be found on devices that launched with Oreo out of the box. The practical reason is that Treble requires two different partitions and older devices upgrading to Oreo will not be able to give these requirements without reformatting. But with the Xiaomi Redmi Note 4 – and evidently now with the Xiaomi Mi 5 – which has an empty partition labeled “CUST”, third party developers have now created a way to bring Project Treble to these phones.
First, they were able to get Treble to work on a Redmi Note 4. Now, the Xiaomi Mi 5 gets some Treble love. The Mi 5 has the same empty CUST partition, so developers are able to use that to install the separate “system” and “vendor” files to make Project Treble work.
But as we said, this project is still in alpha state, so not everything is working quite satisfactorily at the moment. If you want to install this on your Mi 5, check out source link below.