https://github.com/particle-iot/device-os/releases/latest redirects to v1.2.1. So I have grabbed the bootloader and the two OS binaries from github.
Flashing OS over USB in DFU (yellow blink) mode:
> particle flash --usb photon-system-part1\@1.2.1.bin
> particle flash --usb photon-system-part2\@1.2.1.bin
Flashing the bootloader over USB in listening (blinking blue) mode:
> particle flash --serial photon-bootloader\@1.2.1.bin
! PROTIP: Hold the SETUP button on your device until it blinks blue!
? Press ENTER when your device is blinking BLUE
sending file: firstname.lastname@example.org
Next, I went through the steps in my previous post to download, compile and flash the garadget firmware. It produces the same LED blinking pattern as described previously. I found out that the bli k is actually morse alphabet SOS, indicating a firmware issue (https://docs.particle.io/tutorials/device-os/led/electron I also tried to compile with --target 1.2.1 to make sure, but same problem.
The above outcome was reproducable on two separate Photon devices.
Not sure how to use the web IDE at particle.io/build for this. Apparently apps can be shared with a link (according to https://docs.particle.io/tutorials/developer-tools/build/core/ under “Sharing your app”), but I do not have such link for garadget.
Another way, I guess, would be for me to manually copy the content of each *.cpp and *.h file of the firmware into correspondingly named files in te IDE. Not quite sure how to go about with this though, as the IDE seems to define its projects through an *.ino file, which does not exist in the firmware folder.