I was also lucky on this one.

tty CLI

After connecting to the device using the serial port with the screen command:

sudo screen /dev/ttyUSB0 115200

If you can´t see your ttyUSB, try using dmesg after connecting the badge on your computer.

And also check your /dev/ folder

Reboot !

As you can see, behind the badge, there is a reboot button, and I keep pressing it by mistake!

However, after looking at the terminal, I saw the full message and a small help menu before the shell!

As you can see, I can use TAB to autocomplete commands. Maybe I need to found a hidden command which is not displayed with help command ?

After pressing a few keys, I was able to discover the secret command the_sword_of_azeroth!

Flag

Here is the 7th Flag : FLAG-Cl1F0rFun&Pr0f1t