Ultimately, you can’t know someone’s aversion until you ask, and that can be a personal question. My advice is, when in doubt, don’t make the joke.

Fuckin' nothin'.
Asexual joke, What's an asexual person's favorite thing to do in the bedroom?
Five asexual people are playing cards

One of them starts to explain the rules and then he pauses and says
I would say no cheating but there's already five aces at the table
I wouldn't call my marriage a sexual marriage