The Linux kernel that comes delivered with Debian 8 does not have the UAS (USB Attached SCSI) driver enabled.
I found extracting the driver code from the kernel source and creating a DKMS package for it the easiest way to install the kernel module properly.
Build Debian package simply by running dpkg-buildpackage.
This package was built following the eminently useful instructions at https://vincent.bernat.im/en/blog/2018-packaging-driver-debian-dkms