We have recently adopted two feral small cats - about a year old - from a rescue centre. I kept them in one room for 4 x weeks, feeding them v small amounts very regularly - so they think I’m the food lady! - and then loose in the house for another couple of weeks. They are now allowed to come and go freely in and out as they wish and are showing no inclination to wander, despite our initial worries. They now come when called, one is proving very affectionate, the other still wary, but neither of them are ever likely to be ‘lap’ cats and I would still treat the easier one with a degree of caution.
However, they have proved to be very sweet and gentle - in principle! - and amuse us for hours. So feral cats can be ‘humanised’, but it does require patience.