You shouldn’t need developer settings to install, you just need the unlocked bootloader. Sorry it isn’t running on Debian due to the dependency issue, I hate having to suggest Windows to anyone 
You can use the flash-all.sh script, it may be more informative than using the graphical installer. You want the fastboot version: husky · master · ota / release · GitLab Extract the .zip then inspect the flash-all.sh script and then launch it from within a terminal to proceed.