I had 5 30-minute interviews with a recruiter, current team member in role, hiring manager, and other team members. Process took approximately 1 month start to finish (from application send to offer letter).
The interviews were very friendly and inquisitive, all of which were very engaging discussions. Nothing felt like a gotcha question or something meant to trip you up.
The structure of the interviews themselves are available on a blog post on Unity's site, and it mostly focuses on scenario based questions ("Describe a time when..."). There were 5 interviews of this, so make sure you're able to really pull on a multitude of positive and negative experiences from your career.
One note, the references you list will be contacted and will be put through a relatively in-depth call/interview themselves about you. This is obviously for the good of Unity, but make sure you're listing managers who are able to do more than just verify employment periods.