Note: This post is not about the choice of "for vs. to" in general, it's about their use in terms of "ability vs. action".
I am not sure whether I understand the post "is difficult for me" vs. "is difficult to me" correctly. I suppose the conclusion of which is that the following one is more natural.
"English is difficult for me".
"English" there is a language which could be considered a kind of ability/capability.
How about "learning English"? Which might be more like a kind of action. Is it still more natural to use "for" than "to"?
"Learning English is difficult for me".
Another wording might be
It's difficult for me to learn English.
I tried Ngram Viewer but got "Ngrams not found".