Hi,
1. I can use Programmer in nRF Connect for Desktop to flash the hex file (nRF5_SDK_17.0.2_d674dde\examples\dfu\secure_dfu_test_images\ble\nrf52832sd_s132_bootloader_buttonless_with_setting_page_dfu_secure_ble_debug_without_bonds.hex) into my board.
2. I can use the segger IDE to debug ble_app_buttonless_dfu project and check RTT info.
3. Follow the steps in this link, I can finish BLE DFU process successfully :
a. generate key, bootloader, setting_page, application and merge into hex file
b. flash the hex file in to my board
c. generate updated application zip file and do DFU successfully
Now, I connect the board to segger IDE with JLink, it can download but cannot run from main().
I searched some articles and it said the dfu/secure_bootloader have some memory conflict with softDevice. However, I did not see any detailed or easy solution about how to solve this issue. I found this solution and this answer using SDK 15, but some variables or functions have already changed in SDK 17.