If you try to flash Tizen OS (any version) on a new Ubuntu or Debian installation, you will notice lthor no longer plays nice with the Linux kernel, and it will fail without any messages. It has something to do with this.
The problem is /dev/ttyACM0 is no longer detected, if you do a ls /dev/tty*, ttyACM0 is not there even if the device is connected.
Two options:
Revert to an older kernel
Which you shouldn’t do. If you do want to do that … may Linus guide your path.
Install an older version of lthor
Since you’re probably not that crazy to revert to an older kernel, we’ll talk about option 2.
Step 1.
Download an older version of lthor. (current is 2.0, download 1.3 for Debian/Ubuntu here, for Fedora/OpenSuse/ArchLinux, check here).
Step 2.
Put your device into download mode (Power + Volume down buttons), connect it to your computer using an USB cable and type the following commands into your console. No need to reboot, but if you do reboot your computer, you will need to type them again. Or add them to a startup script.
$ modprobe cdc-acm
$ echo "04e8 685d" > /sys/bus/usb/drivers/cdc_acm/new_id
You can start flashing your Tizen device now.