There were a total of two phone interviews. Both were technical, with one LeetCode Easy/Medium problem each.
After the first phone interview, if the interviewer(s) like you, they will schedule a second phone interview. Following this, they will decide whether or not to extend an offer.
OS question.
About LC easy/medium.
The following metrics were computed from 53 interview experiences for the Nvidia Software Engineer (Internship) role in United States.
Nvidia's interview process for their Software Engineer (Internship) roles in the United States is fairly selective, failing a large portion of engineers who go through it.
Candidates reported having very good feelings for Nvidia's Software Engineer (Internship) interview process in United States.