The article recommends Candesartan as an alternative to propranolol. Candesartan is a calcium channel blocker and there are a wide range of similar CCBs which are reckoned to have an anti-migraine effect such as Amlodipine. (Verapamil is a slightly different type of CCB and I believe it is less widely recommended for migraine prevention than it used to be.)
As I understand it the CCBs tend to have have fewer side effects than many other anti-migraine remedies but I have the impression that they tend not to be quite as effective.