Apple will have transitioned all of their lineup except maybe the 26 core Xeon Mac Pro to M1 by then, and the M1 Mac user base will be 20-25 million. Also, despite your 'they had the developer kit. A notice will appear warning you the Dropbox is an app downloaded from the internet. Click Open to continue. Dropbox will then download any necessary updates and then start the installation process. A Dropbox icon will appear in your menu bar, and the Dropbox app will show in your /Applications folder and in the sidebar.
I heard around that putting a Mac in DFU mode is a hit and miss. Well, maybe I’m lucky, but I have a 100% success rate!
DFU M1 MacBook Air or Pro - my method
Plug M1 Mac to host Mac using a DFU cable, such as this one. Make sure you use the correct port.
Shut down M1 Mac
While you hold the 3 keys, press and hold the power button
Release the 3 keys after counting 10 seconds out loud. You’ll see an Apple logo while you count, just ignore it.
Keep power button pressed for 10 additional seconds.
Display stays black, it’s normal.
Now you can use Apple Configurator 2 to restore it! Make sure you use the latest version on the latest macOS.
Box Drive Macos Big Sur
DFU M1 MacBook Air or Pro - Tim’s method
Dropbox Mac M1
Another way from Tim Perfitt:
Turn on the Mac (or leave it on)
Once it starts booting, hold the power/keyboard combo (right shift, left control, left option) until it shuts off
Count to 3
Release all but the power button for 7 seconds (or until it shows up in AC2)
DFU Mac mini
Mac mini are extremely easy. All you need to do is to unplug from power, wait 10 seconds, hold power button, plug power, wait a few seconds for the LED to be amber. See documentation.