I have seen many en passant checkmates, but I have never seen one that was a brilliant move.
Is there any position where giving checkmate by en passant is a brilliant move on Chess.com?
No. Delivering checkmate via en passant is not a sacrifice, and "sacrifice" is part of chess.com's definition of a brilliant move.
From their support pages:
We replaced the old Brilliant algorithm with a simpler definition: a Brilliant move is when you find a good piece sacrifice.
The criteria for a move to deserve a double exclamation mark have to be more than just being the best option in the position --- that's merely not making an error. So there must be some criterion based on further play. But after checkmate there is no further play. So no sort of checkmate move can be a brilliant move.