The Mi 5s and Mi 5s Plus launched late last year and have been updated to MIUI 8.2 but are still stuck on Android Marshmallow. That’s pretty sad considering Android O is around the corner. LineageOS, the phoenix that rose from the ashes of Cyanogen have released LineageOS 14.1 for them.
For those who have been following the community, LineageOS 14.1 is based on Android 7.1. It was already available for the Mi 5s Plus since May but it has just been made for the Mi 5s thanks to XDA Developers member, LuK1337 and a number of other contributors.
The following features have been confirmed to work: boots, WiFi, Bluetooth, Cameras, video playback, audio, sensors and GPS.
To install it, you have to unlock your bootloader first. You can get help doing that on the official MIUI forum. Once you are done with that, download the build and download gapps. Reboot to recovery, flash the latest build and gapps and then reboot your device. More info is available here.