So, I noticed that one of the notice board requests asked for a slave without any requirements. So, I purchased a cheap slave to fulfill the mission, as well as a few others for the ones that did require traits.
The slave I purchased even has combat and working unlocked, but isn't showing up on the list. I suspect this is related to him not being a "Slave" class due to the update on roles (Subordinates when purchased, only Slave if abducted from a dungeon), and the "any" quest wasn't updated to include subordinates (or doesn't say that it has to be a slave; all requests say Slave even if they accept subordinates).