The Citroen DS had a pedal type parking brake and there was a good reason for that. The car had a single hydraulic circuit that operated the brakes, suspension and steering assist. If one of the trillion tubes and hoses developed a leak while on the road, then you would lose brakes suspension and steering in short order.
The parking brake is entirely mechanical and acts on the front wheels using a separate set of smaller pads. If you lose pressure in the main brakes you can use the parking brake to stop the car. Also you can lock the release latch in the open position so the parking brake pedal won’t stay depressed if released, like a normal brake pedal.
I once had the misfortune of losing pressure in my DS. When that happens first the big red stop light in the dashboard turns on, detail here (there’s also a button to test the light, this shows how important its proper function is). When the light turns on you have aproximately 10-20 seconds to bring the car to a stop using the normal brakes. After that, you lose steering assist so the steering wheel becomes very heavy, the suspension drops to the bump stops and the brake pedal doesn’t work at all. If you somehow miss that time window then your only way to bring the car to a stop is with the parking brake.
That day I actually managed to drive the car for 70 kilometers through a winding country back road until I came back home.