That sucks. But maybe I can help you.
I tried a firmware update for the Troodon last year (provided by a Troodon user). This resulted in a badly responding printer and I wanted to go back to the original firmware. Luckily I had made a backup. But I did not know how to place it back.
After some searching I found this link (fallback-procedure #1). It tells you how to install the firmware. The important thing is to turn off the printer and disconnect it from the mains. The procedure tells you that you'll have to remove the SD card from the main board. If you unscrew the right panel at the bottom you will have access to this micro SD card.
After you've copied the files on this SD card and placed it back in the main board, you'll have to make contact with the main board via a PC and a USB cable that you can connect to the backside of the printer. Use YAT to connect to the main board.
A copy of my system files can be downloaded via this link.
Good luck!
I hope that this will at least save you weekend.
Best regards,
Paul
It's a terminal emulator - lets you connect your printer via usb to your computer.
Yep. octoprint is linux based. You can just install it on Debian.