In this video taken from this question, the video shows the pilot using one hand on the yoke and one hand on something else (perhaps the throttle? I'm not a pilot). Is it normal to do landings with one hand?
It is absolutely normal, in fact it's rare for a pilot to have more than one hand on the yoke at any one time as it isn't required. Movies will often show pilots manhandling yokes with two hands, but that's just Hollywood. The only time two hands is required is when extra strength is needed on the controls, for instance a hydraulic failure.
When landing a pilot will have one hand on the yoke (or stick) and one hand on the throttle, as throttle adjustments are needed to maintain the correct glide angle and initiate a go-around if required.
In many many aircraft, from gliders and recreational planes to fighter jets and the whole Airbus fleet beyond the A300/A310 (meaning a very sizable chunk of the airline industry), control surfaces are moved using a stick and not a yoke; in such cases, using two hands is often not even an option.
Also, you often need your other hand for something else (throttle in powered aircraft, brakes in gliders).
Yes, it is normal, and, in most cases, necessary. Control of he throttle is just as critical in such a low speed, low power setting environment as control of the control-surfaces. You need a hand on both. Also, using two hands on the yoke can tend to cause you to over-control the aircraft.
When I learned, I was actively taught to fly one handed, and even then not 1 hand, but a couple of fingers and a thumb. A death grip on the yoke leads to over corrections.
During T&O, your right hand is usually glued to the throttle. It only took my instructor pulling the throttle a couple of times on me during approach/takeoff to learn THAT one.
Left hand - index, middle, thumb on yoke (PTT, electric trim, etc) Right hand - everything else - throttle, flaps, trim.