I've been thinking about aphantasia a lot, because I regularly GM (game master) tabletop roleplaying games. I often tell players at my table to start with a mental image and then I'll help them use the rules to construct whatever makes narrative sense. "Let your vision guide the rules, don't let the rules constrain what you think your character can and can't do." I've tried to figure out what it would mean for my GMing style if I ever had a player with aphantasia.

One thing which I think is often ignored when this topic is discussed is that even for people with vivid mental imagery, many cognitive processes still take place without relying on that faculty. I can remember my birthday without visualizing a calendar; when I want to remember my birthday, the numbers just pop into my mind seemingly from nowhere.

Based on the research in this paper, I could see a few ways to make a ttrpg work for aphantasics: allow time for them to do a quick sketch to figure out what they want, rather than (or in addition to) suggesting mental imagery; avoid metaphors and similes and instead focus on what would be observable facts in a scene; and be prepared to offer more artwork and diagrams from my side to get across my points, instead of relying purely on theatre-of-the-mind.