Among the core conditions for flow, immediate, unambiguous feedback about whether an action is succeeding turns out to matter enormously — enough that a group facing a major sensory limitation still found deep, reliable flow specifically in activities where they could clearly sense their own success or failure, even without visual feedback. This suggests feedback clarity, not the richness or ease of the activity itself, is doing much of the real work in producing sustained absorption.
The practical takeaway generalizes well past this specific population: when a task or hobby feels flat and unengaging, the fix is often not "make it more exciting" but "make the feedback clearer" — restructuring an activity so a person can reliably tell, moment to moment, whether they're succeeding.