Your ECs can be about anything that interest you. Being in a sport (you have Squash), having a job - are all great.
Now, if you can tie together some ECs in a way to show more about you in an essay - then great. But your essay should not be a repeat of what they already see in your list of activities. But for example, my boss - her roots a few generations before her - are in Africa. She goes every two years to what she calls the homeland. She’s very involved in organizations both at work (we have “clubs” for lack of a better word - LGBTQ, African American, Asian American, etc.) and in the community. Perhaps her essay would be about how she’s so proud of her culture and wants to learn more - and she takes her kids every two years to the homeland, etc.
But writing about her engagement in clubs wouldn’t work - because she’s already listed them and her duties, etc.
Being a minority is a hook - but they can no longer use it from the survey (when they ask what is your ethnicity). They can still use it if they find out another way.
Anyway, it’s great that you do stuff you’re passionate about - but it needn’t be connected to your major and that’s not a hook.
Make sure you make your folks aware that an NMSF and your ultimate NMF can get you free or very inexpensive education - just so they’re aware. But it’s awesome if they say, we’ll pay and don’t worry. Some parents may change their tune after though - it’s a $400K delta.
I do think Brown is a reach - but that’s ok - apply and see. And you might look at U of Rochester as a target / back up - they also have an open curriculum and it’s a very respected school.
Or find other schools that are very strong n your area of interest - there are unfortunately less and less schools although most will have anthropology. I was more talking about ethnic studies (the kind of major that is getting cut for low interest).
Best of luck.