DFU-UTIL Issues

There's this:
https://docs.particle.io/guide/getting-started/connect/photon/#installing-the-particle-cli
This:
https://docs.particle.io/guide/tools-and-features/cli/photon/
This:

This:

And this very useful one:

This one in particular for DFU:

So I'd say that there are quite some resources available, all of whom I've used successfully in the past. That said, if you've got any suggestions on how to improve the process, feel free to share.
As to getting it working, I can highly recommend the installer by Mumblepins, which has been really helpful for me in the past.