If the advice to keep your chin touching your front shoulder does not work, then it is time to step back and look for a root cause before trying drills. If your natural off snowboard stance is a bit bow legged and you are in a normal (back foot neutral or forward) stance, you may be better off switching to a duck (back foot negative angle) stance. If your stance is too narrow, you may be subconsciously uncomfortable. Anything that is just a bit off can cause a need to be extra safe that is solved by turning the upper body towards the direction of travel. That's just a natural reaction that is hard to overcome with just a drill. As a last resort or a quick attempt at a fix I will sometimes try simply increasing the stance angle for the front foot. That does not provide much relief on being able to see more forward, but it does lessen the torque on the lower body that twisting the upper body delivers. If nothing works, then it may be time to consider alpine boarding where you have much higher forward stance angles for both feet and the upper body naturally faces almost square.
There are many riders with the style of riding with their hands covering the nose and tail of the board. This can be used as a drill so that the hands provide a visual reference for the shoulder alignment. But it does not force alignment. Hands on the steering wheel works a little better because if you turn your shoulders forward then your front hand comes "off the steering wheel" and ends up on the heel side of the board. Hands on the hips helps to retard the transmission of upper body rotary movements from the shoulder to the feet, but this drill does not work as effectively as hands behind the back. Hands behind the back does not fix shoulder alignment, but it's a good check for one cause of turning the shoulders: missing lower body rotary movements. If it is hard to ride with your hands held behind your back (which limits shoulder rotation) (and I have most of my students ride holding their hands in front first), then you probably don't have enough leg bend movement going to help your legs turn underneath the upper body and you are twisting your upper body to help get your turns started. The simplest drill to fix that is the mantra "rise to start your turn and sink to finish" (sinking to start and rising to finish also works, but is harder to do).
An "evil rusty" drill for developing lower body vertical movements starts with riding with your hands on your knees throughout most of the turn. The exception is when you want to change edges you rise up and touch your hands to the tops of your shoulders (note this drill is not for people who have not mastered toe side turns with a slight arch in their back). After the shoulder touch and edge change you go right back to touching your knees. Shoot for a 90/10 percentage split between touching knees and shoulders. When you've mastered the timing, hold the tops of your boots instead of your knees. When you've mastered that you touch your toes. When you've mastered that you touch the board on heel side and edge grab on toe side. About half the people that try this drill reach their knees by bending at the hips, we try to to encourage less hip and more knee and ankle bend at this point. By the time we get to touching the toes, it's extremely uncomfortable to accomplish this with only hip bend. Once the vertical movement has been accomplished it's time to work on stretching out the movement so that the entire turn is either rising or sinking and synchronizing that movement with turning of the legs underneath the upper boy to help guide the turn. This drill is evil because it is not for fragile people, it's freakishly hard to do without the desired movements/timing and surprisingly easy with the movements/timing.
Riding with the shoulders "open" works. A lot of people do it. It works much better when the stance angle matches the shoulder angle. When those don't match, torque is applied to the lower body and that makes control of the board more difficult. But it still "works". That's why this is something most instructors want to "fix". If the usual drills don't work, then it's time to step back and try to find the underlying cause. You may to need to call in some serious help (i.e. the equivalent of an AASI level 3 cert or higher - I'm only level 2 cert AASI).