Here is a list of known issues and bugs with Debian on the QNAP TS-409:
- The installer fails to make the system bootable, especially on configurations with LVM and RAID. You can apply a workaround.
- There's a timing issue that will result in not all disks being recognized in time on boot. If you're experience, you can use a workaround.
- qcontrol (the tool to control LEDs and beeper) doesn't work.