I have a different experience with foreign languages than most aphants.
I started learning to write software at just eleven years old, before the IBM PC even existed. In high school, I studied German. Probably because a spoken language isn't that different from a software language (other than being, well, spoken), I personally found learning German rules to be intuitive. Thirty-five years later, I still remember all of the syntax rules, though I've forgotten most of the vocabulary, due to lack of practice. But, due to being an aphant, my pronunciation was always bad (I sounded far too similar to English), since I can't repeat in my head how I've heard things pronounced to imitate the correct sound, nor recognize when I say things wrong. So, it turned out I'm excellent at learning to read and write languages, and understanding them is easy for me, but pronunciation is an endless struggle for me.
A year out of high school, I volunteered to be a missionary in another country. When they sent me to Mexico, I spent two months beforehand learning Spanish. In that short time, I became very comfortable communicating in Spanish. I quickly become basically "fluent, but with a bad accent" :p
I've continued speaking Spanish, and despite no formal studies, I read and write it better than many native speakers, and I understand it spoken extremely well. But, like with German, even after 34 years speaking the language, and knowing all the rules well, and married to a woman who speaks it as her primary language, I still sound far too "gringo". Since finding out at the beginning of 2021 that I have aphantasia, I finally know why, but it doesn't change the fact that it's absurdly hard for me to improve my pronunciation. It also explains why I have such difficulty acting as an interpreter between English and Spanish, unless they do it more sentence-by-sentence. When interpreting is paragraph-by-paragraph, it's impossible to not start to lose the content of what was said.
When I ran into a more severe block is sign language. Two years ago, I started working for a company that provides interpreters for calls between the deaf and hearing (acting as their software architect). They provided me with weekly classes in sign language. Besides the fact that I have to put in extra effort to learn new signs, since I can't see them in my head, understanding sign turned out to be a nightmare. Since my mind is trained since birth at extracting meaning from what is said, so I can understand languages (even though I can't repeat in my mind the sounds of what was said), I don't have an equivalent way wired into my head to extract sign language. As they quickly move their hands, I immediately get lost. I'm sure I could get it eventually, but it would probably take an absurdly long time.
It turns out children with autism or similar learn better with "mixed media" communication. I suspect that is true of aphants as well. For example, an elementary school class has been taught where communication is done spoken and in sign language simultaneously. The communication and understanding by the autistics was shown to be significantly better (with no negatives for the other children). That proved there's a good way towards an integration of "normal", autistic, aphants, deaf, and blind students into a common learning environment (and it would help foreign students as well!). But for that to work, the language needs to be "iconic" (obvious gestures, like used in American sports). The downside is that American Sign Language and others over time have become less "iconic", which means that they are non-intuitive for novices. And ASL doesn't really have any technical words, so there's a huge number of words where they instead have to spell it out letter by letter in English (which means it's not really sign language at that point, it's English). That's very unfortunate. The only "iconic" sign languages I know of are Plains Indian sign language (long out of use), and International Sign Language (very uncommon).
The fix would be a new international sign language that isn't meant just for the deaf, but also autistics, aphants, etc. The best starting point would probably be basing it on the words of the language Toki Pona. It's a language with just 137 words that allows basic communication. Giving that a set of iconic signs would create a starting point that would give aphants a way to learn ASL and other sign languages later, since the mind is already trained on how to extract meaning from sign as it happens, as happens with spoken languages.
There is already a sign language for Toki Pona, but I suspect it isn't very iconic:http://tokipona.net/tp/janPije/signlanguage.php