I didn't start learning too long ago so I don't know what a lot of the best Korean resources are. I've just been learning about irregulars, but it hasn't told me how to find out what the exceptions are. I've been struggling with finding a dictionary I can use offline (preferably) with decent UI that tells me these things, and I'd appreciate if someone could tell me
In more than 10 years of learning Korean, the source I've found which best explains 불규칙 (irregular conjunctions) is 'Korean Grammar in Use - Beginning' by Ahn, Lee and Han (Darakwan publishers, Seoul). Each chapter related to verbs marks irregular forms, and there are seven chapters at the end of the book dealing with each kind of irregular form, for example, 바쁘다 > 바빠요. In Korean, the 'irregular' forms are very regular compared to English, changing to either 아요 or 어요 like every other verb. The only difference is that something has been omitted from, or changed in, or added to, the verb stem.