"Their wings are also less severely clipped than they were in the past, giving them a greater ability to fly. Now they can flap up to the roofs of the Tower buildings, and Merlina, the raven most bonded to Skaife, flies so well that she regularly spends time outside the Tower walls. “They need freedom, but they also need protection,” Skaife says of his ravens, as a soldier would speak of the British people. His new regime has been a great success, though changes to the wing-clipping routine have resulted in several chases to retrieve ravens gone awol. One bird was returned to him—alive—inside a gym bag."
https://www.theatlantic.com/magazine/archive/2018/10/ravens-...
There are those who free flight their birds, but that requires lots of training and requires constant monitoring of the birds, calling out to them when they get too far. Birds rely on loud calls to find their way back to their flock (hence why they squawk all the time--its a natural homing beacon meant for large distances).
I'd say semi-clipped wings are probably a good compromise without constant monitoring. These birds will outlive birds in the wild, while still having a greater degree of freedom.
0. http://www.libertywings.com/2008/training/basic-flight-train...
1. https://adventuresofroku.com/blogs/education/free-flight-tra...
Edit: as pointed out elsewhere, wing clipping is not permanent. That's not the point.