My brother is very worried about getting a return offer at Meta - he'll be interning there this summer. He reviewed the videos on Nail Your Return Offer As A Meta Software Engineer Intern, but is still confused on who he would assign to review diffs/vouch for his performance other than his EM.
Some great answers here as well: Advice for getting faster code reviews?
I actually talk about this in the course here: https://www.jointaro.com/course/nail-your-return-offer-as-a-meta-software-engineer-intern/part-6-meta-intern-success-series-how-most-interns-fail/
Your intern manager should give you 2-3 names of teammates who are also open to reviewing your diffs. If they don't, you can just go around the team, meet people, and ask the friendliest ones if they would be open to reviewing your diffs.
A tactical angle is to go through the blame of the codebase you're extending and assigning the people you find there as reviewers. This doesn't just apply to interns either - Any engineer should do this if they're lacking reviewers.
Best of luck to your brother! The course should be really helpful to him. You can refer him to Taro Premium using your referral code: https://www.jointaro.com/rewards/