this method has problema) install userdebug gsi (phh, los, leos etc) with dsu sideloader apk from github
or
b) take any recovery for your phone and change prop values for adb root in recovery
ro.secure=0
ro.adb.secure=0
security.perf_harden=0
ro.debuggable=1
persist.sys.usb.config=adb,mtp
boot into gsi or recovery
adb root
adb pull /dev/block/by-name/boot
change rhe prop of reocovery.img
EX)
chaning prop 12.0.14.4 recovery.img and flash to 12.0.14.5 device is working fine.
but when I flash to 12.0.16.6 device
with same 12.0.14.4 recovery.img
it has bricked.
So I flashed original recovery.img of
12.0.14.4
it is bricked status
So I send china, get mainboard change.
I guess if we want to get boot.img from flashing recovery.img
middle version (14. / 15. / 16. ) is important.