This is a really interesting question. As a Chinese instructor, I often encounter students who have great difficulty learning Chinese characters. It is impossible to say whether any (or many) of these students have varying degrees of aphantasia, but I know certain students' problem relates to mentally mapping Chinese characters because visual aids, which help some other students, only contribute to these students' confusion. It is always a challenge for me to figure out ways of helping these students along (instead of counting on their dogged persistence alone).
I have noticed: students who are engineers (and who have no problem drawing generic diagrams of engines, machines, ships-hence it's questionable whether aphantasia is the issue) have a hard time re-producing Chinese characters, even while they can verbally describe the components of a character (by repeating what they have been told).
One approach I have used as an instructor--and your miles may vary--is to appeal to the logical part of the brain. For example, instead of asking the (perhaps aphantasia afflicted) students to memorize characters by working on the shapes, ask them to find a logical way to organize the characters for ease of memorization. Grouping characters, for example, in a way that works for you (which may not necessarily be encouraged or even approved by your instructors) definitely works. Use a simple character/radical as an "anchor" to trigger memories of additional components (for example, once you write out the "anchor", add a line, add a dot...)
Of course, repetition, like writing something many, many times over, does help, but it can be time consuming and not practical for some learners. But an alternative method, using flashcards--which you manually create yourself from scratch, may work as well as repeated writing practice. You may not be able to mentally form an image of a character, but you may be able to recognize the image/character once you see it. Working with flashcards may be just as effective as writing characters many times over. The emphasis is on flashcards you make yourself from scratch.
A combination of repetition with other techniques probably is your best approach.