Here is a link to a very helpful chart from Metzer farms where you can look at their evaluation of duck temperment - 1 being most calm and 10 being most high-strung. I would say go for a calm breed, but also consider that many of them are the heavy-weight breeds, such as pekins, who come with considerable potential health issues that you will have to learn how to take care of, and also they might not have the most longevity, though they are super sweet. The hard part about getting calls from Metzer is they are unsexed and you may end up with a bad male to female ratio. Welsh Harlequins are calm and a light weight bird. I have black swedish right now and they are very friendly. Keep in mind when making your decision that the male to female ratio is usually one drake for 3-5 females. Also, plan to have a minimum of 3 birds because they are such strong flock animals, if something happens to one of them you don't want to end up with a solo duck.
https://www.metzerfarms.com/compare-duck-breeds.html