Here we want to unroot the device, for whatever reason.

Step 1: Undo Customizations

Remove all your previously installed Android app.

Remove all your customized changes.

Step 2: Undo Launcher Mod

adb shell mount -o rw,remount /system
adb shell rm -rf /etc/dp_extensions/AndroidSettings
adb shell rm -rf /etc/dp_extensions/Apps
adb shell rm /data/system/ExtMgr.db
adb shell rm /data/system/ExtMgr.db-journal

Step 3: Flash official image (modded version)

Download from here and use dpt-tools to flash (i.e. fw command).

Step 4: Reset

In the end, it is recommended to reset the device via initialize DPT in system settings.

Step 5: Undo Diagnosis Mode

It is not recommended to undo the change.

But if you really need to, you need to go into diagnosis mode and do the following (I am not responsible if you brick your device by doing the following but making mistakes):

Edit /usr/local/bin/start_eufwupdater.sh

Uncomment the following part

# dd if=$1 bs=$(($DATA_OFFSET)) skip=1 2>/dev/null | head -c $(($BODY_SIZE)) | openssl dgst -sha256 -verify $3 -signature $SIG_FILE 1>/dev/null
#if [ $? -ne 0 ]
#then
#  echo "Verify failed."
#  exit 0
#fi

Edit /usr/local/bin/updater_check.sh

Comment out the following part

KEY_DETECTION_TMPF=/tmp/keyDetect.log

#########################
# Button check
#########################

# animation hint
epd_fb_test gray DU PART 0 && \
epd_fb_test gray GC16 PART 10 0 50 50 150 50 && \
sleep 1 && \
epd_fb_test gray GC16 PART 10 0 50 150 150 50 && \
sleep 1 && \
epd_fb_test gray GC16 PART 10 0 50 250 150 50 && \
sleep 1 &

# if HOME pressed, go into diagnosis mode directly
busybox script -c "timeout -t 3 keyscan" -f -q ${KEY_DETECTION_TMPF}
grep -Fq "HOME" ${KEY_DETECTION_TMPF}
if [ $? -eq 0 ]
then
  rm ${KEY_DETECTION_TMPF}
  epd_fb_test gray GC16 PART 10 0 50 50 150 250
  initctl start diag
  exit 0
fi

# if POWER pressed, cancel and remove update
grep -Fq "POWER" ${KEY_DETECTION_TMPF}
if [ $? -eq 0 ]
then
  rm ${KEY_DETECTION_TMPF}
  mkdir ${DDAT_MOUNT_PATH}
  mount /dev/mmcblk0p16 ${DDAT_MOUNT_PATH}
  change_boot_mode.sh normal
  rm -rf ${END_USER_UPDATER_PKG}
  local_reboot 1
  umount ${DDAT_MOUNT_PATH}
fi

rm ${KEY_DETECTION_TMPF}

Change back the root password

Edit /etc/passwd and change the line for root $6$i2VmFAOV$sEMLa5no1z... to be the original one.. which I forgot what it is :p see if some other remembered it..