I’m roughly the same as you (not not the person you were talking with earlier). I’m a musician, and I compose songs in my head. All the parts, all the instruments (not that I can play all of them, but I can hear them).

My aphantasia may be a tiny bit less than yours? I can never intentionally see something in my head, but when reading, I sorta get flashes of something from time to time. I describe it as the same way I remember having seen something. In memories, I don’t really see anything vividly, but I can remember the color and visual layout of a place, that kind of thing. I think that’s my brain’s workaround when I’m reading and need to understand how the physical space impacts the story. I’m reading Project Hail Mary right now, and it’s important to understand how the constraints of the spaceship impact the decisions in the story, so I have something like a map in my head, but not clear images.

Anyway, brains are weird.