For a company that doesn’t sit well in the books of hardcore Android fans with respect to Android OS updates, Xiaomi has done a pretty impressive job over the past one or so years.
As of this writing, the company has five devices on the stable version of Android 9 Pie (excluding the Mi MIX 3 and Redmi Note 7 that have Pie pre-installed), but the Xiaomi Mi 8 Lite isn’t among them.
Still, the Mi 8 Lite is high on the list of devices expected to receive Pie, but when this will happen remains a secret only known to Xiaomi. On the flipside, being the developer-friendly device it is, you can already download and install Android 9 Pie on your Mi 8 Lite right away thanks to LineageOS 16 ROM.
This isn’t the official LineageOS 16 custom ROM that everyone is looking forward to, rather, it’s the unofficial version. Since it’s a custom ROM we are talking about here, installing it on your Mi 8 Lite will require a few workarounds, among them an unlocked bootloader, TWRP and Magisk.
The developer notes that this is an alpha build and even though it doesn’t have any major bugs, it is meant for Android enthusiasts. If you are not up to the task, you’d be better off waiting for the official release, which should happen at some point this Q1 2019, even if it’s the beta version.
For more info on this ROM and the download link, follow this XDA thread, where you should also find any help you might need in the process.