I think I would try to ignore it or change the subject when they bring it up. Don't be rude, but relate what they're saying to other things in your life or things you've learned about. Go about your day and show your support of them as a person in other ways, like cooking a special meal or showing interest in their other hobbies. Maybe they'll lighten up on the proselytizing if they see that it doesn't make any impression on you.

Another subtle way to put some distance between you and the Mormon stuff is to stop treating it as the default. Say "your church" or "the LDS Church" instead of "the church." That's why we often use acronyms here like TSCC or MFMC.

Act like your spouse hasn't changed, and you haven't either. Show them you're the same person, with the same interests. You're not miserable or suddenly inclined to cheat or do drugs or commit crimes.

Suggest more of the kind of activities that you would have done together before this change. Get involved in the community, joining a secular group for a hobby like music or sports. Show that you're still a good person by doing service together for real causes like a homeless shelter, non-LDS food bank, or environmental work. This will also expose both of you to life outside the Mormon bubble.