It likely requires studying anthropology.

try out James Baldwin's Another Country?

I recently read "The Cautious Traveller's Guide to the Wastelands" by Sarah Brooks. I didn't especially enjoy it, but it might fit your bill. The setting is explicitly multicultural and incorporates real-world ethnicities, but cultural difference is not an important theme. No stereotypes jumped out at me, although one might argue that some amount of cultural appropriation is necessarily involved when White authors write protagonists of color.

In historical fiction, James A. Michener

For people in the future who find this post, I found a video that I can think explores this question really well: Who Can Write Whose Story?

Like a middle school Wikipedia book report, I've picked out some of his sources as being particularly accessible/helpful:

• Alexander Chee's How to Unlearn Everything
• Who Can Write About What? A Conversation With Roxane Gay and Jay Caspian Kang. (NYT paywalled) (transcript on rentry)
• Writing the Other by Nisi Shawl and Cynthia Ward (book, so no link, but you can find it online)