OK so the pinout is different from nordic dongle. There are couple of dongles on aliexcpress that have exactly same pinout as nordic one so this is not the case. Also it comes with usb bootloader, two different ones in fact as per https://wiki.makerdiary.com/nrf52840-mdk-usb-dongle/programming/ :-)
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
OK so the pinout is different from nordic dongle. There are couple of dongles on aliexcpress that have exactly same pinout as nordic one so this is not the case. Also it comes with usb bootloader, two different ones in fact as per https://wiki.makerdiary.com/nrf52840-mdk-usb-dongle/programming/ :-)
so unless you plan to use SWD for programing and clear everything the most important setting in board file is the storage area so that it does not overwrite existing bootloader.
As per https://github.com/makerdiary/nrf52840-mdk-usb-dongle/blob/master/examples/nrf5-sdk/open_bootloader/armgcc/open_bootloader_gcc_nrf52.ld the bootloader starts at 0xE0000 which is same as nordic dongle. You can take storage layout from this https://gist.github.com/fanoush/c081c1d7c8eb2a4562785bbb684f661e#file-nrf52840dongle-py-L66
You can also take whole file but remove
-DBOARD_PCA10059
and fix LEDx and BTN pin numbers and better change default console toEV_BLUETOOTH
Then after building you need to follow that programming guide for your dongle.