translated from this Chinese forum (Need to install Coolapk's app):
https://www.coolapk.com/feed/437324...yMjNmYTM~&shareFrom=com.coolapk.market_13.0.2
download adb tool,fastboot enhance tool,Oxygen a07' OTA full package(we only need payload.bin),Oxygen a07's ofp package(we only need my_preload folder),cos's unbrick package(we only need oplusstanvbk. img),大侠阿木工具箱
https://optool.daxiaamu.com/wiki_pctool (we only need the driver)。
1: first, use 大侠阿木工具箱 to install driver,connect phone and enter developer mode,open usb debug and enable OEM lock。
execute "adb reboot-bootloader",to let the phone enter fastboot。
execute "fastboot flashing unlock",volumn down,power button。
after entering bootloader,execute "adb reboot-bootloader"。
2:extract Oxgyen a07's payload. bin file,open fastboot enhance,ignore unknown partition,show llog and then flash in payload. bin
3:use fastboot enhance to enter fastbootd mode,the phone should enter language selection,make sure

ignore known partition,then flash the payload.bin from Oxygen a07's package.
4:extract oplusstanvbk.img from Abandon_PHB110_V13_202301030.zip into adb tool's radiofolder。(this is to avoid bootloop)
extract the my_preload folder from the a07's OPF package to adb toolbox folder。(This is the pre-installed software of Oxygen OS)
when in the fastbootd(language selection UI) mode, flash in the following two files,
fastboot flash --slot=all oplusstanvbk radio/oplusstanvbk.img
fastboot flash --slot=all my_preload images
/my_preload/my_preloadxxx.img
5:We can enter oxygen os now,do not insert SIM and skip all the setups after entering the syaem。
enter developer mode,enable usb debug,execute "adb reboot-fastbootloader" to enter fastboot,execture command "fastboot flashing lock",press volumn down and power and lock the fastboot。
enter Oxygen OS again and SKIP ALL THE SETUP steps,
MOST IMPORTANT: DO NOT UPGRADE THE SYSTEM USING OTA!!!!! It will bootloop.