No, they don't have the same meaning. 'Are you into that?' means 'Are you interested in that?', with regard to a particular subject or activity. We use this to talk about people's hobbies and interests. 'Are you after that?' is not a common phrase, and it can't - as far as I know - be used to mean the same as 'Are you into that?'. Colloquially, if you say that you are 'after' something, this can mean that you are looking for something. For example, if someone comes into a room and starts looking through all the cupboards and drawers, another person could say 'What are you after?'. So, 'Are you after that?' could possibly mean 'Are you looking for that?'.

"Are you after that" is not a phrasing that I have heard before. One could employ it I suppose, but I think that a literalism would allow one greater freedom of expression. Example: "Is that one of your interests?" "Are you involved with any of the arts and crafts?" "Are you interested in arts such as calligraphy?" "One of the pastimes that I never found interesting was putting puzzles together." "Is calligraphy one of your hobbies?"

I would not use either of these expressions. First, "Are you into that?" is idiomatic. Literalisms give one a greater command of the language. So factually, people do not get "into" things. Idiomatic expressions become "trite"; which is to say, overused. I would construct my sentence as follows: Electronics is one of my interests. Business is one of my interests. or, One of the interests that I pursue is charcoal drawing. or, My favorite pursuit is reading fiction. "One of my passions is watching current events on the TV News programs. Swimming is my favorite recreations. As for leisure activities, I like to attend chess tournaments.