LineageOSrom.net - Currently only available fir Umofficial release of Lineage OS 14.1 for Xiaomi Mi5s. This ROM still under development. So sort of time you'll probably found some bug. See this is not for noob. If you insist to onstall this built, the you take your own risk. The download link are provided below:
Lineage 14.1 Xiaomi Mi5s ()
You will need Google Apps Package too. Donwload link for ARM64 PICO are provided below:
Download GApps Lineage ROM
If you want more suitable package for you, go to list of gapps page and choose what you need.
Instalation need Custom Recovery. Using TWRP is always the best choice. Search carpicorn twrp and instal it into your Xiaomi Mi5s first if you don't have one.
Back-up whole rom (nandroid back-up) and flash both zip file (rom and gapps) after factory reset.
Wait until done and reboot to system after wiping dalvik/art cache and cache.
To enable native root read post about how to enable root access on lineage os without flashing.