If the eccentric phase of the deadlift is done properly, it’s no more dangerous than lifting the bar. In fact, it’s less dangerous.
The lowering portion of the deadlift should be done the same way as a properly performed concentric: in two phases.
First, you lower the bar from the finish position to just below the knees, exactly as if you were doing a Romanian deadlift. This means pushing your hips and knees back as the bar slides down your thighs. Getting the bar past the knees should be easy since, by the time the bar reaches the knees, they’ve been pushed back out of the way, and the tibias are perpendicular to the floor.
Next, you switch to a squat. Simply keep bending the knees while your torso is at a fixed angle, then bring the bar to the floor.