As far as I understand, the nRF52840 USB dongle can be flashed via USB if there's a DFU capable bootloader installed (and it booted *into* that mode).
Once I got the dongle I was able to successfully do so. However I'm kinda lost with how to re-flash it - now it has (custom) software flashed, hence, not being in DFU mode anymore.
Is there actually a way of re-flashing the nRF52840 USB dongle - without hardware interaction (e.g. pressing a button) - once it's running custom firmware? Mentioned custom firmware is mine, so I can implement whatever needs to be implemented in case that helps making re-flashing via USB possible.