Is there a way I can produce a binary firmware file that others can upload to their device without using an IDE? What tool would they use?
You need to create an .uf2 file from your binary firmware file.
Then others can put the RAK4631 into UF2 mode (double press reset). A new drive will appear on the computer. Then people can just copy the .uf2 file to that new drive and it will be automatically flashed.
Adafruit has a short tutorial how to create an .uf2 in their bootloader repo.
Thanks for this, I’ll give it a try later.