Is this (1) devouring the bodies of slain enemies, (2) raising a lower class of people as meat animals (or buying their spare babies à la Jonathan Swift), or (3) eating some of the flesh of honored kin? Or any of the above? Or are they eating tissue cultured human flesh, and does that count as “cannibalism”?
It could be any of those, or even eating the god-king in times of public disaster, as on Navabharata. Most of these stock features are best left a little bit general and vaguely-defined so that someone dealing with generator output can adjust them to fit.
Slightly more generally, there is the traditional SF notion that as uneducated labor becomes less valuable it will be forced into increasingly dystopian circumstances or eliminated all together. Flat Black has lots of interesting high DL planets that do strange things to compensate for this, but I am unaware of one where this particular trope is in effect. Given the limited number of high DL planets to play with and the terrible implications, this is fine. On the other hand, dumping the PCs into a Robots of Dawn style planet with 50 remaining humans and huge amounts of automation might be interesting.