Is it possible to flash a hex file to an electron via USB?
not sure if that’s possible but you can use converter and then Particle CLI
particle flash --usb firmware.bin
The .hex files are for use with a debugger. For Gen 2 devices, this can be a ST-LINK or ST-LINK clone USB stick. For all devices, it could also be a Particle Debugger or Segger J-LINK.