Upgrade Android Nougat 7.1.1 Download Lineage OS ROM for Xperia Z5 (sumire). But please have it noted ti your head guys/girls, this ROM is Unofficially build by developers wich is not officially aligned with Lineage Teams. And it's still in Nightly stage to be frank. Latest update of Lineage OS ROM for Xperia Z can be download below if you insist intalling this Lineage ROM.
Then declarated "YOU ON YOUR OWN" don't blame me for anything your doing. You're not KID anymore, ain't you?
1. Download LineageOS Xperia Z5 Nougat 7.1.1
Download Lineage OS 14.1 Xperia Z5
2. Download G-Apps Nougat for Lineage 14.1
Download GApp Lineage 14.1
3. Installing LineageOS to Xperia Z5 Devices
You need TWRP recovery
Download TWRP Recovery For Sumire Devices here
Recomended reading : Enable Native Root on Lineage OS or replace it with SuperSu