The board came pre-programmed for MBED. I don't need that, wood like to enable regular JLink. I believe the process is to get it in boot loader update mode (hold boot/reset when powering on), and drop special firmware image onto the auto mounted "Bootloader" folder. But where shall I get that special boot loader image?
On the paper sticker it says "PCA10036", and there is a serial number.
With the same setup, I have nRF52840 DK working just fine.
Thanks,
Sergey