Debian 8.3 came out today. As part of this update, Debian installer images for QNAP TS-109, TS-209 and TS-409 are available again. These devices are pretty old but there are still some users. We dropped installer support several years ago because the installer ramdisk was too large to fit in flash. Since then, users had to install Debian 6.0 (squeeze) and upgrade from there. When squeeze was removed from the Debian mirrors recently, I received mail from a number of users.
I investigated a bit and found out that we can bring back the installer thanks to XZ compression and some other changes. The installer is available for jessie and stretch.