Here are flashable zip file wich installs latest Sony stock 6.0.1 Marshmallow ROM 23.5.A.1.291_R3D (VMo AU-NZ), SuperSu v2.76 and latest TWRP 3.0.20 with read and write acces to system. Because device is Wi-Fi only region doesn´t matter. Only difference is bloatware. Since Sony hasn´t push update to SGP511 I use SGP512 firmware which is working fine on my device. If you want you can edit build.prop file in /system -folder to correct model number as shown in screenshot.
Here is the link for new 6.0.1 firmware:
MD5 is: D3B78445485765AB7BD3A163F2A6C4BD
Make nandroid backup before flashing.
Install it by flashing whole zip file via custom recovery. TWRP recommend. If coming from .570 or .575 firmware dirty flash with art/dalvik cache wipe is okay.
If coming from older firmware factory reset is most likely necessary with cache and dalvik/art cache wipes but anyhow recommend. If you want you can restore your data with TWRP after installation and reboot. This install compatible busybox. If you install incompatible busybox you may loose acces to TWRP.
After flashing .zip file if you are getting bootloop you have atleast two choises.
- With pc and Flashtool use your firmware original ftf -file and flash it by excluding "FOTAKernel", "Partition" and "System". In other words in "exclude section" tick these and don´t wipe anything. (Credits @AlanDS)
- Or download "bootloop fix" from here: https://mega.nz/#!BUxFxSAR!bPVEEDnsP...47N0fhA80ltEvw
(Credits @niaboc79 and @machao44) and flash it with TWRP
Here is the old 23.1.A.1.28 (Customized NCB) FTF -file link:
For SGP511: https://mega.nz/#!sVIn1IJI!Ywqoksuej...jWr_mbonMd6PPk
MD5 is: aab7e5728dccb59d44d5ebe38c34c8da
This version of firmware should be rootable. For instructions and download go here: http://forum.xda-developers.com/crossdevice-dev/sony/root-how-to-root-5-0-lollipop-t3212108
Credits: @Androxyde @Chainfire @[NUT] @IaguCool @zxz0O0 @Wolfbreak @shoey63 @serajr @championswimmer @russel5