As a novelist with aphantasia myself (I wrote about it here: https://medium.com/human-parts/im-a-novelist-living-without-an-imagination-358739d6cc83) I'm always excited to meet others who have had similar experience. I've got no voice/internal monologue either, but I love writing dialogue just like you; sometimes I wonder if I should try my hand at plays or screenplays, since they prioritize the parts of the story I love most.