NRF Connect SDK with UF2 Bootloader

I am having troubles flashing applications based on the NRF Connect SDK (Zephyr) on my nRF52840 MDK.

The nRF52840 MDK is listed as supported board for Zephyr.

I am using the blinky example: docs.zephyrproject . org/latest/samples/basic/blinky/README.html

I am using the docs.zephyrproject.org/latest/boards/arm/nrf52840_mdk_usb_dongle/doc/index.html board definition as target for my build.

The build runs just fine, I was able to convert the resulting zephyr.hex using the provided python script yielding my flash.uf2 which I copied on the flash drive. The drive disconnects, the device restarts but now instead of running the application, the RGB LED is continuously pulsing red.

I noticed that using the nrf52840_mdk board definition, CONFIG_BOOTLOADER_BOSSA_ADAFRUIT_UF2 — Zephyr Project Documentation was set to y in my project configuration which seems just fine?

I also tried converting and flashing the blinky example hex from the nRF52840 MDK GitHub repository which seems to work fine, the LED is blinking in different colours. However, that sample is based on the NRF5 SDK, and I am not able to figure out the difference.

I noticed that the python conversion script outputs a different starting location for the application, 0x1000 for the working, old NRF5 SDK example and 0x0c00 for my NRF Connect SDK sample.

I’d be extremely grateful for any kind of advice or pointer towards the right direction. I suppose the flash layout needs to be updated, but that is over my head at this point.

I have now learned that according to Building a hex and UF2 file for the Adafruit nRF52840 Feather Express with Visual Studio Code - Nordic Q&A - Nordic DevZone - Nordic DevZone the issue may be that the NRF5 SDK is using a softdevice while the NRF Connect SDK is not. Therefore, it may be required to erase the entire flash of the device and essentially get rid of the UF2 bootloader as well, meaning that I will have to use a J-Link to program the dongle.

Is that assumption correct and is programming using a programmer even possible?