This technique reminds me of kasina meditation, I haven't practiced it, but but I have read about cases where people developed hyperphantasia.
Wow, in summary what does the practice look like? What do you do?
So, first thing, I have this inner monologue talking to me everytime. I have to first shut it up. This happens when I'm very relaxed and don't think about anything. Then, I slowly focus on the visuals I see (which is nothing). Then, suddenly some shapes come and go, and I try to keep them in my head as much as I can. To influence a flow of visuals, I look at a light and close my eyes. You see the afterimage of the light (which is a "eye" thing, not a "mind" thing). However, this has helped to start seeing some stuff in the mind, even though it takes 10-20 minutes of focus (and mentally exhausting!)
Also, this subreddit has many information and anecdotal experience on this technique: https://www.reddit.com/r/CureAphantasia/
I have seen some shapes and a few colors for now. Most importantly, I have started to see vivid dreams in the last few days, which has never happened before (before that it was just a feeling not a visual. However, my father suggested this might just be that I have learned to remember dreams more by becoming more conscious about it, which is a possibility). It's too soon to judge. So, I'll keep doing it for a couple more weeks to see if it can help me see visuals rather than random flashes.
Try using flickering lights with closed eyes. Around 10hz they create strong visuals after about a minute
I'm aphantasic, though I'm not entirely sure that I have always been that way. I've recently been using Lumenate to meditate, and while it hasn't actually changed my aphantasia (yet?), I do get very strong abstract visuals when using the app. It's closer to the kind of thing you might see while on mushrooms than any kind of physical form. I absolutely suck at meditation usually as I just cannot switch off the inner voices, this seems better as it gives me something else to focus on.
The article mentions Image Streaming, which I've been practising since. Interestingly, it seems to work! I've have been seeing vivid dreams, and have been able to randomly visualize shapes. Nothing to prove it "cures" aphantasia, but we'll see :)