In a Bdieved situation, may non-dairy milk (soy milk, almond milk, cashew milk, oat milk) be used for Havdallah? I recently moved back home and my father does this (almond milk specifically). I dont think Im going to be able to get him to make it on something else (he doesn't want to use wine, juice, coffee, or tea) and I don't want to rock the boat if I don't have to... Am I yotzei Havdallah this way?

Thank you for your question, You don't have to tell your father anything, but I recommend that you should try to make your own Havdala, using grape juice or wine, and of course, try to avoid insulting him. From a halachik point of view, your father does have some sources to rely on but 'l'ehatchila' one should not make Havdala on those types of milk that you listed. See shemirat shabat kihilchata (60: 3-6) All the best!