I gave up on using the GMMK 2 Installation guide and used
When I got to flashing, I used
I skipped over using “Flashing Your Keyboard with QMK Toolbox” It just didn’t work for me.
I moved to “Flash your Keyboard from the Command Line”. Using the command line looks scary, but is actually simpler.
I don’t know what the git command does, but flashing firmware worked without it.