I'm pretty sure you can regain the ability. Covid damages the brain, and the brain "forgets" how to do certain things (like smell or visualise or focus), but brains are incredibly powerful and flexible, and can re-learn these things. I myself have long covid and lost a lot of sensing ability, but have been able to improve my senses of smell and touch by training with promising results. Here are some techniques people have used to help learn/relearn how to visualise: https://www.reddit.com/r/CureAphantasia/
Thanks for trying to help! I answered in another comment, so you can see a better reply there, but I've been trying (a lot) of these things and the short version is that it seemed to work when my brain had been given some time to heal, but repeated covid infections might have made it permanent in my case, or at least given the prospect of future infections. But time will tell. My smell/taste survived the last infection(s?), so there might be some hope that it gets milder.
It's so weird, as I know exactly which "muscle" to trigger to make it happen, which I guess someone having aphantasia wouldn't instinctly know, but it just doesn't do much.
-edit-
Oh, forgot to mention, in the beginning when I trained on visualizing again (back when it did work), I got _so_ exhausted in my brain afterwards, it was like really trying to used some damaged "muscle". I find that really fascinating. I'm not able to invoke such exhaustion in other ways, that quickly.
I was aphantasiac(?) most of my life and I self discovered similar techniques to what they discussed in the Reddit while learning multivariate calculus. I was trying so hard to visualize the integrations and using the “fuzz” I see when I close my eyes to infer the shapes then one day I could actually see them in my minds eye. I never applied the technique to other things because I didn’t have the same motivation to practice that induced my first breakthrough but I am pretty confident the technique works. The plasticity of the brain is remarkable and it’ll adapt to what you need it to do if you work at it.
Can't hurt to try, right?