OpenEmbedded "poky" with some sysmocom specific modifications. Mostly used only up to sysmocom release 201310, but the "pyro" branch is still used for 201705
The concept of directdisk image is overhauled as we are now
having a initramfs that can flash the next image through USB.
The dedicated E1/IP images are rarely to never used and did
probably bit-rot. For the next time we provide such a system
we can simply (write a script to) install the additional feed.