Where to get information about weddings in other cultures?

I'm currently working on a product in the wedding space and I would like to design it in a way that is compatible with as many cultures, ethnic groups, religions, countries, and social classes as possible.

I plan to include a feature where users can provide feedback saying I am missing something relevant to them, but I would like to make an effort to include material for a wide variety of users at launch.

I have found various wikipedia articles and subreddits, as well as a couple of books, but I'm worried that they are misleading. For instance I have read about supposed traditions in my culture that none of my friends or family have ever heard of.

My current plan is to compile a list of as many different demographics as I can think of, and then try to interview (or send a questionnaire to) members of those demographics. However, I don't know how to find these people, how to generate the list of demographics or how to make it worth their time.

Possibly free access to my product could be an incentive?

My other idea is to submit one or more posts to reddit asking for both legitimate traditions and common misconceptions.

Does anyone here have any ideas?