Leeco s2 upgrade 16.0 has finally arrived but upgrade installation isn’t automatic. First I decided to install latest twrp custom recovery so I followed lineageos install custom recovery instructions.

Allow android debuging - see lineageos setup adb. It is Android debugging switch under Developer options.

adb devices
List of devices attached
cd6ab2fd	device

Enter into fastboot mode.

adb reboot bootloader

Verify fastboot recognises my phone

fastboot devices
cd6ab2fd	fastboot

flash the recovery

fastboot flash recovery ./leecos2upgrade/twrp-3.3.1-0-s2.img
Sending 'recovery' (24618 KB)                      OKAY [  0.776s]
Writing 'recovery'                                 OKAY [  0.372s]
Finished. Total time: 1.159s

I verified I can boot newly flashed twrp recovery image holding Volume Up + Power.

After that I followed upgrade instructions.

Running sideload command raised an root privileges error:

adb reboot sideload
'adb root' is required for 'adb reboot sideload'.

I booted into recovery mode and started sideload from there.

adb reboot recovery

Now go into Advanced / ADB Sideload, start sideload and then send needed files via adb. I chose to install MindTheGapps and addonsu too. Start sideload is needed for each file to sent.

adb sideload ./leecos2upgrade/lineage-16.0-20191230-nightly-s2-signed.zip
Total xfer: 1.00x
adb sideload ./leecos2upgrade/MindTheGapps-9.0.0-arm64-20190615_031441.zip
Total xfer: 1.01x
adb sideload ./leecos2upgrade/addonsu-16.0-arm64-signed.zip
Total xfer: 1.37x

One need to pay attention to messages on mobile after each sideload. I really don’t know what happened, but first time I rebooted mobile got stuck in lineage os logo for about 30 minutes. After that I aborted whatever was going on there, rebooted and tried to repeat sideload. Sideloading of lineageos image now ended with error 7 each time. I fiddled with couple of things in twrp. Final steps what helped me was probably Wipe / Format data followed by Advanced wipe with Dalvik / ART Cache, Cache, System, Data checked on. After that sideloading of files ended up with succes and next reboot took just couple of minutes.

I checked install twrp app before reboot on the first try and skipped it on the second try. This could make a difference too but don’t know for sure.