The new patch has introduced the option to hire unequipped recruits for food. The recruit pool is supposed to refresh every three days. However, doing missions resets the timer on getting new recruits.
HOTFIX - v1.0.58929 - 17/06/2020
Fixed an issue where the Base Recruits timer would reset after completing any mission.
We will fix it in a hotfix. Probably this Thursday.
Until then there is a workaround: If you do not do any mission for 3 days the recruits will appear. Since then they change every 3 days even when doing missions.
I was wondering why it always showed 3 days to a new recruit. This makes sense.