I'm also aphantasic and dream normally, and I once got really into lucid dreaming for a ~semester in college.

My best successes would occur after drinking a cup of coffee and immediately taking a nap before a study session.

It was great, I "learned how to fly" and could "morph" my dream into whichever direction I wanted.

One thing stuck out though: whenever I would try and focus on something, I would see a black dot enter the center of my vision. The more I tried to focus, the larger it got. If I focused on an area attentively enough, such that the black circle became all encompassing, I would wake up.

After a few times of this, I could start to notice the focus, and then sort of relax out of it, and thus continue the dream.

It feels like the black dot is my real-life vision coming into focus, and "winning" over the visual aspects of the dream. It's always continuous from black dot to eyes opening.

I rarely lucid dream now, but I've noticed a similar thing happen whenever I try to read text - the black dot appears and I wake up.

Wish I still had unlimited time to go back to sleep!