<p>I was just looking at this too.</p>
<p>It looks like we can use the pre-programmed USB bootloader with Nordic's <code>nrfutil</code> but the usage is a bit nonobvious mostly because it supports signing and the documentation isn't focused on command-line flashing. I found <a href="http://www.d0d0.pro/index.php/2018/09/23/programming-the-new-nordic-chip-nrf52840-and-usb-dongle-board-pca10059-featuring-it/" rel="nofollow">this flashing guide</a> that makes quick work of it but I have yet to install python2 so I can try it out.</p>
<p>Also here's a <a href="https://www.rototron.info/circuitpython-nrf52840-dongle-openocd-pi-tutorial/" rel="nofollow">post</a> on using openocd with it that includes some good information about things you might encounter when wiping the bootloader.</p>
<p>It's my understanding that one could easily backup the bootloader with openocd and restore it later but I haven't confirmed that.</p>

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