Struggling to distinguish Northern vs. Southern phonology in listening practice

I’ve been learning for six months using materials that seem to mix Northern and Southern accents, and it’s killing my listening comprehension. When I hear 'd', 'gi', and 'r' all pronounced as /z/ in some clips but as /j/ or /r/ in others, I get completely lost. Should I just pick one regional variant of Vietnamese to focus on exclusively for now, or is there a way to train my ears to handle the code-switching early on?