The DOOGEE S51 version is updated as follows：
Flash tool operation is recommended to experienced users only. If you are not yet an experienced flash tool user, please carefully read the flash tool tutorial before proceeding, and strictly follow each instruction.
Except if an authorized or responsible expert directly asked you to do that,
never format the flash chip of your device or you instantly lose your warranty!
DOOGEE S51 receives all updates automatically via FOTA method. You need this tool only in case of emergency (if you've bricked your phone), if you want to apply a clean install or if you want to clear all root access and custom recovery to make your phone able to receive FOTA updates again. Moreover, flashing with SPFT is the only option to repair (replace) damaged system software.
Flashing tool link：https://1drv.ms/u/s!AvX9KABcpSV1mEagE1JGzMWrxHLT?e=CRch58