Hi Kinky,
i sadly had to replace KGPE-d16 board for my fileserver to a Supermicro A1SRi-C2558 because of electric pill ....
investigating a bit with intelmetool and mecleaner non of them could found any sign for an ME-region in this board.. so i asking myself if there is no ME/SPS on the intel C2000 socs, what would make them a DAMN SEXY platform to port coreboot too.
to answer your other question: yes the Intel Rangeley (C2000) is the last/newest SoC what does not include a ME(like) subsystem.
Unfortunately the SoC has a fatal hardware bug: https://www.extremetech.com/computing/244074-intel-atom-c2000-bug-killing-pr...
But this hardware bug has resurfaced on some of the later ATOMs aswell.
There is a Golden Master Image for coreboot from intel, but it's probably not publicaly available, OTOH if you want to work on Rangely, there should be someone on this list, that can arange for you to get this "drop".
Another pointer: https://mail.coreboot.org/pipermail/coreboot/2017-March/083712.html
Cu, Goetz.