No matter whom you may ask, you will get the same answer.
Traditional grammar asks us to say "No matter WHOM you may ask,...", but in modern English, I wonder whether it is grammatically acceptable to say "No matter who you may ask,...".
No matter who(m) you may ask, you will get the same answer.
You are right: traditional grammar says that it should be accusative (objective) "whom" because it is the object of the verb "ask".
But nowadays it has become acceptable to use nominative (subjective) "who" as an alternant to "whom", especially in informal contexts.
Older speakers (like myself) tend to cling on to traditional "whom", but the fact that "who" has become generally acceptable to many speakers can't be ignored.
So use whichever one you feel most comfortable with.